Germany's highest court said Wednesday that Parliament must have a bigger say in euro zone rescue packages, in a landmark ruling that may make it more difficult for Europe to respond swiftly to the debt crisis.

The Constitutional Court rejected a series of lawsuits filed by euroskeptics aimed at blocking the participation of Europe's biggest economy in bailout packages for Greece and other euro zone countries, as had been expected.

But it said the government must seek the approval of parliament's budget committee before granting aid and spelled out that the ruling should not be misinterpreted as a blank check for future rescue packages.

The constitutional complaint has been rejected, said the president of the court, Andreas Vosskuhle, in a ruling closely watched by policymakers and investors because of its impact on the decision-making process in the 17-nation currency bloc.

This was a very tight decision. But it should not be mistakenly interpreted as a constitutional blank check authorizing further rescue measures, the red-robed judge told the plaintiffs, government officials and members of parliament in the courtroom in Karlsruhe.

Greece, Portugal and Ireland have already received aid from Europe and the International Monetary Fund while Italy -- the third largest economy in the euro zone -- looks increasingly vulnerable as it struggles to implement a savings program.

The prospect of having urgent rescue decisions bogged down in legislation in Germany -- and potentially other euro zone parliaments, if more states follow suit -- will not please policymakers trying to streamline that process.

Chancellor Angela Merkel already faces a revolt in the Bundestag, the lower house of parliament, over European leaders' decision in July to grant new powers and extra funds to the current bailout fund, the European Financial Stability Facility. The  issue goes to a vote on Sept. 29.

Parliament also has to ratify by the end of the year the fund which will replace the EFSF from mid-2013 -- the European Stability Mechanism -- and the court ruling is likely to influence how it allocates rescue funds in future too.

(Reporting by Annika Breidthardt; Writing by Stephen Brown)