A last-ditch attempt to stop British ratification of the Lisbon treaty was being planned in the Lords last night as EU foreign ministers vowed not to let Ireland's “no” referendum kill it.

The Conservatives will table an unusual motion today urging that the third reading of the European Reform Treaty Bill, due tomorrow afternoon, be delayed, probably until the autumn.

They are seeking the support of Liberal Democrat, crossbench and even rebel Labour peers to back the measure, arguing that they would not be stopping ratification altogether but delaying it while Ireland and Europe decide what to do next.

David Miliband, the Foreign Secretary, flew back from the foreign ministers' meeting yesterday to tell the Commons that the Government believed ratification should continue as planned.

The Lords motion is likely to be tabled today by Lord Howell of Guildford, the former Cabinet minister and chief foreign affairs spokesman. It is being put forward as a way of peers stopping short of killing the Bill by voting against the third reading, but responding to the Irish decision.

Ireland pleaded for time yesterday to work out if it could save the treaty. Ministers from the eight member nations yet to pass the treaty were urged by their colleagues to continue their ratification processes, which will pile pressure on Dublin to try a second referendum next year.

Irish ministers are considering whether they can rerun the vote but said that they needed a calm analysis of the reasons for the “no” vote, an approach which suggests a delay of at least a year.

The treaty aims to streamline decision-making in an enlarged EU of 27 members, with the loss of national vetoes in many areas, the creation of a president of the European Council and a smaller European Commission.

It is already the product of a two-year “period of reflection” after the French and Dutch voted against the EU constitution in 2005, with most of its provisions salvaged in the new document.

The intense pressure on Dublin to rescue the Lisbon treaty was shown yesterday when Angela Merkel, the German Chancellor, seen as the treaty's main architect, declared: “The EU needs the Lisbon treaty to be able to act.”

EU foreign ministers in Luxembourg did their best to play down talk of a “two-speed Europe”, an idea suggested at the weekend by Luxembourg's Prime Minister, Jean-Claude Juncker, which would leave Ireland behind if it abandoned the treaty.

Brian Cowen, the Irish Prime Minister, expected to present ideas on the way forward to Thursday's EU summit in Brussels, discussed the Lisbon treaty impasse with Gordon Brown yesterday in the margins of a visit to Northern Ireland by President Bush.

President Sarkozy of France said yesterday: “I would like to travel to Ireland to find out under what conditions we could minimise this problem [of Irish rejection].”

Mr Sarkozy said that he saw it as his duty to avoid a European institutional crisis during France's turn at the EU presidency, which starts next month.

In the Commons, Mr Miliband said that 18 countries had approved the treaty and Ireland had “set out clearly” its respect for the right of other countries to complete the ratification process. “An Irish vote is determinant of an Irish position but cannot determine the ratification decisions of other countries.”

He added: “This Government believes ratification should proceed as planned.”

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