The formal opening of accession talks with Turkey in London due to begin on Monday would mark a pivotal moment in the development of the European Union. Turkish membership would alter the character of the EU more profoundly than the accession of any other country in almost 50 years. It would extend the EU some 900 miles to the east, taking its external frontier to the borders of Syria and Iran. It would bring into the EU some 70 million Muslims, profoundly altering its demographic and cultural profile and admitting a country that would soon become the EU’s largest member.

The opening of accession talks will also be the most substantial achievement of Britain’s otherwise lacklustre EU presidency, a step to which this country has been committed for longer and more wholeheartedly than any of its partners. The nearer the formal start comes, however, the greater the dissent, backsliding and outright opposition to Turkish membership by EU governments and fretful publics. Yesterday the European Parliament postponed ratification of the customs union — a prerequisite of full EU membership — and added two conditions to entry talks: that Ankara recognise the present (solely Greek) Government of Cyprus and that it acknowledge the killings of Armenians during and after the First World War as genocide.

The conditions, as provocative as they are politically disingenuous, pander to an increasingly hostile EU opinion by citing issues that appear reasonable but are calculated to anger Ankara. The same is true of those European politicians, especially Angela Merkel in Germany and Nicolas Sarkozy in France, who are now talking of “privileged partnership” as a substitute for full EU membership. The phrase may sound emollient, but it signifies a dishonour-able reneging on past promises and a humiliating rejection of Turkish aspirations for the past 42 years. “Privileged partnership” is knowingly vacuous, offering no decision-making powers and little more than the vague relationship promised to Russia, North Africa and the Middle East by the 2003 European Neighbourhood Policy.

What politicians in Strasbourg, Paris and Berlin are hoping is that a piqued Turkey will itself flounce out of the talks. For what they fear has, at heart, little to do with agricultural costs, Turkey’s human rights record or the tortuous Cyprus negotiations. It is, more crudely, the atavistic clash of civilisations — the contention that a Europe based on Christian values and culture has no place in its midst for a Muslim nation. Beneath the rumblings in France, Germany, Austria and the Netherlands also lie popular hostility to Islam and a rejection of any more Muslim immigration.

To reject Turkey on these grounds is not only dishonourable but wrong; it is to ignore the entire Atatürk legacy and the huge strides that Turkey, as a secular nation (as are also all the members of the EU), has made towards democracy. Of course there is a way to go. But it is the promise of membership that has removed the death penalty, upgraded civil status laws, expanded minority rights and overhauled the criminal code. If the EU now reneges on its negotiating framework, it loses all power — unprecedented in Turkish history — to influence domestic policy. Difficult details, such as freedom of movement of labour, can be worked out in the lengthy accession talks. What cannot be worked out is any alternative to immediate talks on full membership.