Leading article: An appeal to the lowest political denominator

Bulgaria and Romania are due to become full members of the European Union next year. Regrettably, this new expansion is being greeted in Britain not with the enthusiasm it deserves, but with an increasingly intemperate discussion about how to limit the rights of these new EU citizens. Where the last expansion - when the EU went from 15 to 25 members - was hailed as a vindication of the European project, this new stage is being broached with undisguised trepidation.

The Conservative Party's immigration spokesman, Damian Green, came straight out with it yesterday and called on the Government to limit the numbers of Bulgarians and Romanians who would be permitted to work in Britain. He said that ministers needed to learn the lesson from the "unprecedented numbers" who had come to Britain after the admission of Poland, the Czech Republic and other smaller countries two years ago.

Mr Green's remarks, in a BBC interview, were the latest sign that the Conservative Party may be starting to succumb once again to the fatal lure of the immigration card. Given David Cameron's efforts to end his party's reputation as "the nasty party" and present a new, modern face of "compassionate Conservatism", this suggests a worrying reversion to type.

Almost worse, however - because it implied that ministers may not be above playing the immigration card either - was the Government's initial response. The Secretary of State for Trade, Alistair Darling, stressed that no date had yet been set for the accession of Bulgaria and Romania, but that there would be no "open door" policy. He went on to talk about the need for "proper management" of the system, "so that we can take care of all the other things we need to consider, like the healthcare system, the education system and so on".

Mr Darling's mention of health and education suggested that ministers are now so concerned about warnings of over-stretched public services that they believe it politic to be seen accepting them at face value. Far from assuaging concern, though, such talk will only stoke the flames. Much like the Home Secretary's recent call for a "mature debate" on immigration, Mr Darling's response implied that there was a down side to immigration, while making no reference at all to the up side. This panders to the lowest political common denominator and shows a lamentable lack of leadership.

Any attempt by Britain to impose restrictions on Bulgaria and Romania that were not imposed on the previous 10 newcomers will be found insulting and discriminatory by those countries. Already, there are resentful claims from Sofia and Bucharest that any restrictions on their workers' mobility are essentially motivated by racism.

Mobility is one of the greatest assets of the European Union and one that has been a boon to the British economy. Two years ago, Britain was one of only three existing EU countries - the others were Ireland and Sweden - not to introduce quotas for new EU citizens seeking work. This was a brave decision, but it was also a wise one.

It is true that the number of workers from the "new" Europe coming to Britain for work has vastly exceeded early estimates, but the great majority have been successfully absorbed into the economy. The benefit has been theirs, and ours.

Mutual interest dictates our welcome for the next "new" Europeans. Anticipation of Bulgaria's EU accession has already encouraged adventurous Britons to buy holiday homes there. Bulgarians and Romanians should be free to earn a living in Britain. We expect them to fare just as well as the Poles, Czechs and others who are already here.