A German member of parliament from the opposition conservatives will challenge Germany's planned approval of the EU constitution in a bid that could delay ratification of the charter.
Peter Gauweiler, of the Christian Social Union, will present his case to Germany's top court on Monday and wants parliament to postpone indefinitely its intended passage of a bill to approve the constitution.
The EU charter has so far been ratified by six of the EU's 25 member states, but its future is in doubt with opinion polls indicating France will reject it in a referendum due to be held on May 29th.
Germany's lower house of parliament, the Bundestag, aims to ratify the charter on May 11th in a move the government hopes could give a boost to the French "Yes" campaign.
Mr Gauweiler said he wanted a German referendum on the issue.
"The German Bundestag cannot give away to the EU more rights than it has itself," he said in a statement, adding many MPs had similar reservations. "Such a far-reaching constitutional law can only be based on a referendum of the German people."
However, the government has ruled one out, saying Germany's constitution does not allow for a national vote on the EU charter.
The Bundestag is due to debate a motion today calling for a referendum brought by the Free Democrats, the smallest of Germany's main opposition parties, but that is expected to be rejected, including by Mr Gauweiler's own CSU party.
An opinion poll published yesterday showed broad support for the EU constitution in Germany. Some 47 per cent of Germans back the document, compared with 20 per cent who reject it, the survey for Internationale Politikmagazine found.