MPs have raised concerns that the "ambiguous" wording of the EU reform treaty could be putting the sovereignty of Parliament at risk.

Ahead of the ratification of the document, the Labour-dominated Commons European scrutiny committee called for it to be debated on the floor of the House.

The Conservatives used the report to step-up their calls for a referendum on the treaty.

"This is a damning rejection of the government's arguments by a Commons committee with an inbuilt Labour majority," said shadow foreign secretary William Hague.

Committee chairman Michael Connarty said the European Commission and the European Court of Justice would acquire more power over justice issues.

"The process could not have been better designed to marginalise the role of national parliaments and to curtail public debate, until it has become too late for such debate to have any effect on the agreements which have been reached," the committee said.

The MPs also said that drafts seen since their October 2 report - which described the new treaty as similar to the failed constitution - are "substantially the same".

Connarty said that despite the government having secured the right to "opt-in" to justice and home affairs matters, it would still involve transferring jurisdiction from the UK courts.

"There are also new and unquantifiable risks which may be incurred by future decisions by the UK not to opt in," he said. "These matters should be debated on the floor of the House before the treaty is signed."

The committee also raised concerns that there was no opt-out from the new Charter of Fundamental Rights, saying that Britain would need to comply with rulings by the European Court of Justice even if there was a UK protocol.

"Despite expressing our deep concerns that the government argue boldly for a form of words that would put the sovereignty of the UK Parliament beyond doubt, there is still ambiguity in the draft treaty on whether a legal obligation is being imposed on Parliament in respect of its proceedings," Connarty added.

"This is not an area in which any ambiguity is tolerable, and we look to the government to deliver on its undertaking.

"We also retain serious doubts about the effectiveness of the protocol on the charter, and conclude that despite the government strengthening control of the 'opt in' arrangements, there will be a steady transfer of jurisdiction to the Commission and the European Court of Justice in the areas of civil and criminal justice."