Challenges to the government's refusal to hold a referendum on the Lisbon treaty will "come to a head" in the House of Lords next week, the Conservative leader in the House of Lords believes.
Lord Strathclyde claims a Liberal Democrat abstention and the support of crossbenchers would be enough to defeat the government when the EU (amendments) bill comes before parliament's upper house.
Tory amendments to be laid down on Wednesday will demand a referendum on the EU treaty agreed by European leaders. Before that, a Monday vote will relate to parliamentary control over further extensions of the EU's role in UK politics.
Lord Strathclyde says the Lords has a "constitutional" obligation to challenge the government on the issue. He says people feel "betrayed" because there are no current plans to put the Lisbon treaty to public opinion.
The government promised to hold a referendum on the EU constitution, which was abandoned after being rejected by French and Dutch voters in 2005. It says a vote is not needed on the Lisbon treaty because of its significant differences to the constitution.
Lord Strathclyde disagrees. "Line by line debates in our House have demonstrated unequivocally that the new treaty is to all intents and purposes the same as the previous one, and transfers major powers from our parliament to Europe," he said.
"The central role - and I would argue duty - of an independent second chamber in our constitution is to ask the Commons to think again in such circumstances."
Whether Tory peers will succeed in defeating the government rests on the Liberal Democrats. Unfortunately for Lord Strathclyde, a Lib Dem spokesman told politics.co.uk his party's peers would support the government.
This has frustrated the Conservatives because it means Lib Dem peers are not following leader Nick Clegg's party line in the Commons.
Lib Dem amendments laid down in the House of Commons are now being brought forward by Tory peers in the Lords, forcing Lib Dem peers to vote against amendments moved by their party colleagues in the lower house.
As a result Liberal Democrat peers have described amendments whipped by their colleagues in the lower house as an "elephant trap" and a "blunderbuss approach", the Tories point out. The Lib Dems have accused the Tories of "playing politics" with the issue.
"The Commons have made their views known on this, and we're just following the views of the Commons," the Lib Dem spokesman said.
Nigel Farage, leader of UKIP, told politics.co.uk: "On day one of the debate in the Lords the Lib Dems said they would vote with the government on this issue - stacking the numbers against us.
"This followed a three-line whip for an abstention in the Commons, which was a pretty cowardly act even by the Lib Dem's high standards.
"The fate of the great British public rested with the Lib Dems. The honest thing to do was to not take a stand, to listen to the debate and go into it with an open mind. The way they've done it is dreadful really.
"Our hopes now rest with the Irish," he concluded, referring to the upcoming vote on the treaty.