Mr Blair is guilty of playing to the gallery of popular prejudice

It comes to something when France has to rescue British politicians from their follies. But this is what happened yesterday, on the first day of the European summit in Seville. A meeting originally intended to smooth out some small wrinkles about EU enlargement and cap Spain's EU presidency with a show of unanimous bonhomie has had to find room on its agenda for the subject of the moment: immigration and asylum – an issue on which centre-left governments have come to grief all over the Continent.

There are two ways of interpreting what happened yesterday. The more charitable one is that presented by the Foreign Secretary, Jack Straw, who said that Europe was united on the need for a tougher stance on illegal immigration, but that there was no question of cutting aid provision to poor countries. Instead, the EU would agree to provide "incentives" to countries that complied with immigration requirements, first and foremost by agreeing to take back their nationals who had tried and failed to obtain asylum in EU countries. According to this version of the truth, nothing could have been further from British intentions than depriving already impoverished countries of cash.

The second, and regrettably more probable, version is that the British and Spanish, with Italian support, did indeed favour cuts in aid provision, if only as a headline-grabbing earnest of their intention to clamp down on illegal immigration. The intervention by the Secretary of State for International Development, Clare Short, who said that it would be "morally repugnant" to do this, demonstrates that this was indeed an option being considered in London and constituted part of Britain's opening position at Seville.

Regrettably, the question that then arises takes us straight back to the politics of spin and all the suspicions that Downing Street hoped it had quashed by staging Thursday's prime ministerial press conference. Did the British Government canvass aid cuts in the serious expectation that it could join forces with Spain and Italy – governments of the right, both – to have the measures adopted as EU policy? Or did it rather advance the proposals in the firm belief that they would, in fact, never be enshrined in EU policy because of French and other objections?

The first would suggest naivety; the second, a lamentable and cynical desire to play to the gallery of domestic prejudice. For the fact is that, while cutting aid might look like punishment from the perspective of Europe, it would not have the slightest positive effect on illegal immigration and the consequences could be extremely negative.

Many of the countries least receptive to taking their illegal migrants back are not, in fact, recipients of European, or any other, aid. They include China and Sri Lanka who want proof that the immigrants are really their nationals; the would-be migrants know that and regularly destroy their identity papers. The adjustment of trade incentives – the proposal likely to be adopted at Seville – is the only realistic measure at the EU's disposal, and not a very effective one at that.

But it took France – with its newly elected centre-right government, let it be noted – to point out the obvious. Depriving needy countries of already inadequate aid will only reduce the opportunities in these countries even further, encouraging more people to seek a future elsewhere. It may be unpalatable to right-wing governments in countries where the threat from the further right is real and where foreign aid is the very lowest public-spending priority. For Britain, however, and for a centre-left government with a massive majority, the question should never have arisen.