The Constitution treaty is signed but, in Belgium anyway, ratification in a referendum appears unlikely.
Prime Minister Guy Verhofstadt has lost the political backing he needs after the Spirit Party, one of his coalition partners, dropped its support.
The party fears the referendum could be hijacked by the far-right Vlaams Belang Party campaigning against Turkish membership of the EU.
Spirit Party Chairman, Geert Lambert, said the debate so far in Belgium has not been about the Constitution but about eventual Turkish EU membership.
With the opposition Socialists also against the referendum, Verhofstadt no longer has the backing he needs.
The decision by Geert Lambert’s party is a dramatic U-turn.
“We are changing our minds because we feel that some people wish to abuse the idea of a referendum,” he said. “I won’t let my political thoughts be violated by one particular party, which has a totally different aim.”
Spain is holding a referendum on February 20.
In the Eurosceptic UK, meanwhile, the bill paving the way for a referendum is not now expected to become law for another 12 months.