"Considering the size the EU has reached today and the debates held in the past over enlargement, any additional enlargement demands particular attention", especially if it would considerably change the EU's internal balance, reads an explanatory summary for the tabled amendment.

The provision which appears to be clearly targeted at EU candidate Turkey with its population of 70 million – was opposed by the French Socialist Party (PS).

It "in reality only stigmatises Turkey," Socialist deputy Pierre Moscovici was quoted as saying by French daily Liberation.

"One cannot treat a country of 70 million people like this, it is lamentable," he added.

After the debates on the constitutional reform proposal and its amendments in the French Assembly, the text will be brought before the French Senate and a final decision is to be taken by a three-fifths majority of the two bodies gathered for a Congressional meeting in July.

Previously, the government had approved scrapping an obligatory referendum clause introduced in 2005 by the then president Jacques Chirac, who had made the move in a bid to reassure France's public opinion on Turkey's EU future and to increase the chances of a Yes vote in the upcoming referendum on the EU constitutional treaty.

The reform proposal to this clause would have let the French president decide on how to ratify a country's accession to the EU in the future - as has been the case to date.

The options would be to either hold a referendum, or to leave the decision to the French Congress where a three-fifths majority would be needed for it to pass.

But according to media reports, French President Nicolas Sarkozy, who is a staunch opponent of Turkey's EU membership, yielded to pressure from UMP deputies and gave his blessing to the new text currently under discussion.

Ukraine as collateral damage

Besides Turkey, if eventually integrated into the French constitution, the amendment could also affect EU hopeful Ukraine, which has some 46 million inhabitants.

The proposal comes as a cold shower to the large eastern European country which wants to be part of the EU club and had recently expressed high hopes for progress on this issue during France's stint at the EU helm, starting I July.

Kiev believes it has become "hostage" to certain member states' reluctance to have Turkey in the EU.

"Unfortunately, Ukraine has for a long time been an indirect victim" of bids to stop Turkey from eventually becoming an EU member, a Ukrainian diplomat told EUobserver.

"The rules should be equal to everyone, it is unfair to have one rule for one set of countries, another rule for other countries," he added calling the French proposal "quite artificial" and "unhelpful".