Vigil of the dinosaurs as big beasts vie to outlast each other in Lords

The Deputy Prime Minister angrily attacked peers in the House of Lords who are engaged in a war of attrition with the government over the Parliamentary Voting System and Constituencies Bill.

The sedate environs of the Lords have rarely seen such a show of strength as the government and opposition eyeballed each other, waiting for the first to break.

But with the clock ticking on the Constituency Boundary and Referendum Bill, the government pushed through an all-night session on Monday to try to make sure the committee stage was completed in time.

If the committee stage fails to finish by today it means the alternative vote referendum cannot be held on 5 May.

An attempt at a compromise of splitting the constituency redraw and the voting referendum had failed as had possible changes to the bill, so the two sides dug in overnight.

Beds were set up in the committee rooms for tired peers, and the coalition parties organised a stack of magazines for them to read and wile away the hours as they dragged on through the night. But there were signs yesterday evening that the reading matter had been used up and the government benches had already had enough as a second planned all-night session was cancelled.

Mr Clegg conceded the battle with the Lords had meant the legislation had "somewhat stalled" but stressed: "It will be passed. We are determined that it shall be passed."

The ninth committee day on the bill, which has already cleared the Commons, began at 3:48pm on Monday and did not end until 12:51pm yesterday.

The House was restarted at 2:15pm for the introduction of three new members and oral questions before peers were back on the main item on the agenda and dealt with three sets of amendments. They adjourned at the unusually early time of 4:34pm.

Although the atmosphere was noticeably more co-operative than on Monday, it remains unclear whether the government will succeed in its aim of having the legislation on the statute book by 16 February.

That is the deadline required for a referendum to take place on 5 May, as the government intends, on a move from the "first-past-the-post" system of electing MPs to the "alternative vote" (AV) system.

Peers may face another late night tonight when the 11th committee day begins at 3:30pm. The Lords must not only complete the committee stage of the bill but its report stage and third reading before it can become law.

During rowdy exchanges in the Commons, Mr Clegg rounded on Labour leader Ed Miliband, accusing him of "weak political leadership".He complained that some former Labour MPs who he accused of being "monosyllabic" in the Commons had become "verbose" in the small hours of the night.

It appeared last night that the government may make concessions on redrawing the boundaries and reducing constituencies.