In future an immigrant arriving in Germany and wishing to stay may have to sign an "integration contract". That is the idea of the Integration Minister, Maria Boehmer.

The contract would set out basic German "values," including "freedom of speech" and "equal rights for women". The idea behind this is the club: if you join you have to accept the rules. "Anyone who wants to live here for a long time," says the minister, "and who wants to work has to say 'yes' to our country".

In different forms ideas like this are surfacing across Europe. The concern is that significant parts of European cities exist as "parallel societies". There is not a shared identity and so there is not a common citizenship. Politicians are concerned that if communities do not relate to each other it is easy for rumour and prejudice to flourish.

Initially one of the basic tenets of multiculturalism was that newcomers brought with them their own culture, which was respected. Increasingly, however, the mood is changing - migrants are expected to integrate and embrace a country's basic values.

The French are currently debating national identity and emphasizing "core values". The French President, Nicolas Sarkozy, has said that all beliefs are respected in France, but "becoming French means adhering to a form of civilisation, to values, to morals".

The French Immigration Minister, Eric Besson, said "we must reaffirm the values of national identity and of the pride in being French". He wants the Marseillaise to be sung as often as possible and the French flag flown. A parliamentary commission is looking into banning the burka - the veil that covers everything but the eyes. The French president has already given his view that "France is a country where there is no place for the burka".

Britain, too, has introduced citizenship tests. Migrants have to take language and citizen classes designed to help them integrate better. Only the other day Prime Minister Gordon Brown said that "British people want to be assured that newcomers will accept the responsibilities as well as the rights that come with living here, obeying the law, speaking English, and making contributions".

Identity has been a subject that politicians have been wary of but now, as a subject, it has become mainstream. Across Europe they detect voter unease and they want to head off that concern finding expression with extreme parties.

In 2001 I covered riots in the northern British town of Oldham. The far right acted as provocateur, but a mainly Muslim enclave called the Glodwick estate battled with the police. Five years later I returned. What struck me was how separate the communities had become. As far as I recall, the school in the estate did not have a single non-Muslim pupil.The headteacher told me that she could not talk to some of the mothers because they rarely left their houses. Occasionally the children were put on a bus and taken to another part of town so they could meet children from other cultures.

What rarely happened was that a child would go to a friend's home after school and so experience and enjoy different traditions. Now the situation there may well have changed, but I encountered a concern then about "parallel societies" - that they could not just be breeding grounds for myths about others but that they weakened the idea of the common bond.

It is natural for immigrants, when they first arrive, to want to live amongst their own community. It is often the only way to find work. In New York you still find a significant number of Irish or Italians working in the fire department or the port authority. But the vast majority of arrivals wanted to become "American" and to embrace their new country with all its customs and values.

In Europe the views of the ethnic minorities differ hugely. A poll in France found that only 4% of Muslims there want to live exclusively among other Muslims. In Britain some migrants from Pakistan and Kashmir are more cautious about living alongside other communities in the giant melting pot that is Britain today.

In Switzerland this weekend voters will be asked to decide whether to ban the construction of minarets. There are only about 300,000 Muslims in the country and many of them are from the Balkans and so do not practise Islam. But a handful of minarets has become an issue. As has happened before in Switzerland, the debate is surrounded by controversial posters, including one showing a woman in a burka standing by a Swiss flag flanked by minarets which look like missiles.

I covered the last similar referendum in Switzerland. Then the immigrant was portrayed as a "black sheep". Many rejected the tone of the debate, but it was not difficult to find people fearful that their known world was disappearing, that their national identity was being diluted.

So, across Europe, there is an active debate as to whether more should be asked of migrants to embrace the societies they are joining.

