The Tories say there should be a referendum on the treaty
Conservative hopes of forcing a referendum on the EU treaty have taken a further blow after Lib Dem peers said they would vote against one.
Lord McNally, Lib Dem leader in the Lords, said they would not be asked to abstain like their MP colleagues.
The Tories had hoped Lib Dem peers would help force a referendum back on to the agenda after it was rejected last month in the Commons.
Lord McNally said he wanted to avoid "elephant traps" set by the Tories.
But Shadow Foreign Secretary William Hague said the Lib Dems' position on Europe was "now in total chaos".
"They now have a three-way split between rebel MPs who want a referendum, Lords officially voting against a referendum and a leadership lamely abstaining.
"Nick Clegg's authority over his party now looks very weak indeed."
The UK Independence Party described the Lib Dem move as an "awesome display of cowardice".
In a joint statement, UKIP peers Lord Pearson and Lord Willoughby de Broke, who both spoke in the Lords debate, said: "We have always known how fanatically pro European the Liberal Democrats have been and today they certainly demonstrated that."
But Lord McNally said he wanted to avoid any confusion about the Lib Dem position on the Lisbon treaty.
He told peers: "Let there be no doubt that we on these benches want to see this Bill passed and this treaty ratified.
"Our general election commitment to a referendum was on a constitutional treaty. That commitment died with the constitution which was rejected by the French and the Dutch.
"We have taken the view that the present treaty is an amending treaty which should be carried through by the Parliamentary process."
He added: "The Conservatives have gone on about a referendum but when my colleagues in the Commons offered an in-or-out referendum, they ran away from that."
About 70 peers were scheduled to speak in Tuesday's European Union (Amendment) debate - but Baroness Thatcher, who made a rare appearance in the chamber at the start of proceedings, was not among them.
Opening proceedings for the government, Lords leader Baroness Ashton said the Lisbon treaty was necessary to streamline and reform EU decision-making.
It set clearer objectives for the EU and would make the EU more transparent and accountable to the member states, she told peers.
She added: "For the first time, national Parliaments will get a direct say in making European Union laws.
"Also, for the first time, the Lisbon Treaty defines the EU's competencies, setting out explicitly where it can and cannot act."
But Conservative peer and former Chancellor Lord Lawson said the treaty would do precisely the opposite of that, describing it as an "anti-constitution".
He said the delay between the collapse of the original treaty and the creation of the Lisbon Treaty showed the EU could manage without it.
But a number of senior Tories spoke out against their party's policy.
Ex-Chancellor Lord Howe said he did not have "huge affection" for the "complex" treaty but failure to ratify it would be a "serious blow to the credibility and effectiveness of the United Kingdom".
Ex-EU commissioner and former home secretary Lord Brittan said he was "strongly opposed" to a referendum.
He said: "The treaty is useful and necessary and does not radically transform the EU or our relationship with our European partners. It is not a constitution."
But former Tory Home Secretary Lord Waddington said: "Respect for Parliament will continue to decline so long as our leaders don't play straight with the British public.
"It is our plain duty to hold the government to its promise about a referendum. If we are not prepared to, we might as well pack up and all go home."
'Matter of trust'
Lord Dykes, winding up for the Lib Dems, criticised the Tories' "pathetic hatred" of Europe and said his party was "ready to take on all comers" in promoting the UK's role in the EU.
Lord Hunt of Wirral, for the Tories, said: "I hope ministers will approach the amendments tabled in this House in an open way."
He described the issue of whether there is a referendum on the treaty as "a matter of trust" and said that it was in fact Nick Clegg who had first suggested a referendum in 2003 and the proposal was later taken up by Mr Blair.
The Bill was given a second reading unopposed after a marathon 12 hour debate.
There is likely to be a vote on a referendum at a later stage in its passage through the Lords.