Perhaps the reasons are best demonstrated by Nicolas Sarkozy's latest and somewhat silly pronouncement on the subject. The French President has joined Angela Merkel and David Cameron to declare that multiculturalism has failed.
Up to a point, Nicolas. For there is surely one small problem. It can hardly have failed in France, since France has always consistently been the major western democracy which has been most insistent that multiculturalism would never be tried.
And this allows us to ask a pertinent question which might help the crowded out centre to get a hearing: was Britain or France more or less successful in seeking integration?
Clearly, the French have always placed enormous emphasis the core values of an indivisible Republican citizenship, and the symbols of national identity, which the Tricolore fluttering from every town hall. There is a strong political consensus on this Republican model, cherished by the French left as well as the right. If those are the secrets of success, along with loud proclamations about the dangers of multiculturalism in encouraging separation and segregation, then we can reasonably expect proudly anti-multicultural France to be the most integrated society in Europe, and a shining model for us all to follow as we ditch multicultural doctrines in pursuit of integration.
So, are they? I very much doubt it.
Sarkozy may be credited with seeking to use his powers of patronage to promote a more ethnically as well as gender balanced team at the top in France. He has to do it like that, because you will search the French National Assembly in vain (except for those representing overseas territories) for the counterparts of the black and Asian Labour and Tory MPs who had a strong presence in the Parliamentary Class of 2010. The British children of the 1970s, who grew up in the multiculturalism era, seem to have made much faster strides at integrating, and competing on equal terms in the political elite than their French peers.
Perhaps the biggest issue is about which country is doing more to deal with social exclusion, unemployment and poverty. Here, the truth is that France's particularly strident anti-multiculturalism has run so deep that it makes a definitive social comparison difficult. It would famously offend against the Republican philosophy of integration to even collect the information which would be necessary to inform any serious study of the successes and fallures of how integrated (or not) France actually is.
Sarkozy now says that ""We have been too concerned about the identity of the person who was arriving and not enough about the identity of the country that was receiving him". Quite how and where this concern manifested itself in France is somewhat less clear. So perhaps Sarkozy should one day pause and read his own speeches for a reminder of the problems that this deeply felt theoretical commitment to integration has created for any practical agenda to pursue and secure it.
Unlike in Britain or the US, where people are often asked to tick a box about ethnic origin, in France it is illegal to classify people by ethnicity or to ask census questions on race or origins. The foundation stone of the secular French republic is that all citizens should be equal and free from distinctions of class, race or religion.
Sarkozy recently went further than any other French president to denounce the hypocrisy of everyday racism and discrimination, which has poisoned that republican ideal. He said the lack of data on ethnic minorities was hampering the ability to measure inequality and deal with it.
Meanwhile, race campaigners describe a society plagued by discrimination, where non-white French citizens with "foreign-sounding" names are routinely discriminated against in education and employment, or targeted by police stop and searches. Even state housing authorities have been found guilty of denying flats on the grounds of race. Yazid Sabeg, a businessman of Algerian-Berber origin appointed by Sarkozy to advise on tackling discrimination, will today launch a commission to examine ways of officially collecting statistics on France's ethnic make-up for the first time. But the proposal has created such a political row that it is unclear whether Sarkozy could shelve any future plans.
French discourse, the term ethnic minorities is not common, with habitual references to immigrants and immigrant-descended populations. This is itself a potentially segregating discourse. (I was pleased that the Daily Mail accepted my criticism of its complaint about the descendants of immigrants being counted as British in official statistics).
Far right leader Jean Marie Le Pen embarassed himself in 1998 by declaring that black players could not feel patriotism for France. The multi-ethnic team's victory in the World Cup was heralded as a significant moment for French society more generally, but the feel-good factor faded without noticeable evidence that it had secured integration. Even as World Cup champions, 36 per cent shared Le Pen's view that 'there were too many players of foreign origin in the French football team'. The National Front continues to criticise the French team as too multi-ethnic to be considered French. Meanwhile, from a British perspective, it is surprising that French-born Cameroon footballer Benoit Assou-Ekotto expressed surprise in a Guardian interview last year that his black British Spurs team-mates naturally thinking of themselves as English.
Assou-Ekotto is beginning to look ahead to the World Cup finals with Cameroon. Although he was born in France and has a French mother, there has never been any issue over his allegiance. Like many young people in France born to an immigrant parent or parents, he feels that "the country does not want us to be part of this new France. So we identify ourselves more with our roots.
"Me playing for Cameroon was a natural and normal thing. I have no feeling for the France national team; it just doesn't exist. When people ask of my generation in France, 'Where are you from?', they will reply Morocco, Algeria, Cameroon or wherever. But what has amazed me in England is that when I ask the same question of people like Lennon and Defoe, they'll say: 'I'm English.' That's one of the things that I love about life here."
Multiculturalism can encourage or even incentivise difference, if it leads us to think that we would get a greater share of attention and resources on the basis of ever narrower identities - as Gujeratis, Somalis and so on. But the French experience suggests that a strident and patritotic anti-multiculturalism can encourage difference and fail to promote a common identity too, if too many people from a minority background do not feel that it is about them.
My argument is not that Britain got everything right. I think it is fair to say that British multiculturalism did not always value integration enough, though integration was part of the motivation too, certainly for Roy Jenkins. We have a confident celebration of multiculturalism in London and big cities, some segregated and fractured towns, and a sense of displacment and loss often in some of our least mixed areas.
The common framing of this debate as a choice between prioritising social/economic or symbolic integration is mistaken. Both matter. We need to recognise that integration is a two-way street. It does require allegiance and commitment from all citizens to shape and observe the values and rules of a shared society, as well as action on the social and economic agenda to ensure that the promise of integration is met and experienced as a social reality.
So where did integration succeed in Britain?
Firstly, the history of Britain is largely the history of successful integration. Perhaps that's why we don't notice it. But just about every one of the institutions of which we tend to be proud has been the product of immigration and integration - not just the NHS, but also the Ashes-winning cricket team, and the Army, and even the German-Greek infusions to the Monarchy. Though the headlines will always stress the flashpoints over the complex, everyday story of how we live together, our history should give us confidence that integration is possible.
We became a much less racist society. As John Redwood generously noted in response to David Cameron's speech, the political left in Britain did a good deal to delegitimise racism (though this important broad social change was not the achievement of the political left alone). That makes it less difficult to articulate the shared content of a common citizenship too. No European society has eradicated racism, including ours of course. But the established high profile presence of the French National Front has been among the factors to legitimise a level of racially charged language in mainstream political discourse that would now seem very unusual in the UK.
Still, I am quite open to the argument that it is time to move on from multiculturalism. There has long been an important and sympathetic critique of the limits of multiculturalism, which has been crowded out of discussion as the mood darkened after 9/11 and 2005, even though it provides some of the foundations around which we could construct common ground, rather than argue over the meaning of words.
Multiculturalism may perhaps have been an important and necessary phase, but it always risked underestimating the shared cultural reference points in the era of post-war immigration and exaggerating our differences. We seem to forget, because of our amnesia about Empire so that history began with Britain's Finest Hour in 1940, that Britain's multi-ethnic society grew out of a shared, if contentious, history. My parents are from India and Ireland. Its not a coincidence that I am British rather than French. And, as Andrea Levy's Small Island captures brilliantly, the Windrush generation of post-war immigrants had rather more in common with their new host country, even if that was often not recognised given the more visible differences of skin colour. If human rights are the essential foundation, we might be more careful about the difference between welcoming cultural diversity and seeming to endorse cultural relativism.
Whatever its strengths and shortcomings, for me, the biggest weakness was that - despite all efforts to the contrary - it remained too often perceived as a debate of minorities, for minorities and about minorities. We can not construct a common citizenship where the majority are not sure whether and how they fit in - and it becomes ever more apparent that the controversies and confusions over what we are talking about mean that the frame of 'multiculturalism' is bringing us ever diminishing returns.
So Britain might want to move on from multiculturalism to strengthen a shared citizenship, because it didn't get everything right, but we also have the resources to move on because very often it did help us to integrate too. And perhaps the British and the French might one day see the value of the point that the other side stress, and converge somewhere in between. For France will need to work out where its very different model of integration succeeded and failed too. They will never be in favour of multiculturalism, because they never have, but they might perhaps reject the word and think about the value - as a resource for integration - of perhaps just a very little bit more of the thing itself.