Peers endured their latest finish yet over key Brexit legislation as they pushed debate through until the early hours.

The House of Lords rose at 2.37am following approximately 10-and-a-half hours considering the European Union (Withdrawal) Bill line by line for a sixth day.

Around 25 peers were in the chamber as proceedings concluded, with one peer at one stage battling to stay awake before rallying to continue listening intently as the sitting dragged into the small hours.

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Shadow foreign affairs spokesman Lord Collins of Highbury thanked Government chief whip Lord Taylor of Holbeach for ensuring there were “so many” peers in the chamber for his speech.

He joked: “At one point I was slightly anxious that I would be speaking to an empty House. But it really does cheer me up to see so many noble lords here at this time.”

The debate started shortly after 3pm on Monday, stopping only for 60 minutes to allow peers to consider the Salisbury nerve agent attack and have a short break.

Day six of the Bill’s committee stage saw peers consider devolution, transport, insurance and various other issues.

Tory former cabinet minister Lord Forsyth of Drumlean warned proposed changes to the Bill, which transfers EU law into UK law, would hand a veto to Scottish ministers and mean “the tail wagging the dog”.

He argued those seeking to amend the proposed legislation, requiring the consent of devolved governments, were “naive”.

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Lord Forsyth added Scottish nationalist politicians were engaged in “political gamesmanship”, whose ultimate goal was to “destroy” the UK.

The former Scottish secretary said: “We are faced with an administration in Scotland which is absolutely determined to break up the United Kingdom.

“That is their purpose. They can have all the talks till the crack of doom with the political administration.

“But the politicians have another agenda… which is to destroy the United Kingdom.”

Lord Forsyth hit out at the “the posturing of ministers in the Scottish government which is about trying to create division, turn everything into a constitutional crisis”.

He added: “This is a lot of heat and waffle perpetrated by people who don’t like the results of the referendum and who are terribly keen on referenda but find it very difficult to accept the results of referenda.

“This amendment would give a veto. It would mean the tail was wagging the dog.”

There was also a blue-on-blue spat when he took a sideswipe at fellow Tory peer Baroness McIntosh, who supported the amendment, accusing her of “pursuing her ideological determination to reverse the decision of the British people”.

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This was rejected by Lady McIntosh, who said: “I have always considered myself to be a pragmatist.”

She added: “I also think it’s very unfair to impugn a position to a party that is not actually represented in this house and cannot answer back to any of the allegations that were made.”

She argued the proposed change to the Bill “goes to the heart of consent and trust”.

Former diplomat Lord Kerr of Kinlochard, who authored Article 50 that triggered the formal Brexit process, also referred to Lord Forsyth’s contribution as the “pyrotechnics from the pyromaniac”.

During the debate, Tory former minister Douglas Hogg, the Viscount Hailsham, also raised concern over sections of the Bill which seek to transfer European law into domestic UK law.

The peer told ministers that by not consulting devolved administrations more widely on the transfer of laws, it could “stir up nationalist opinion”.

Earlier, Brexiteers and Remainers in the Lords united to press the Government to accept updated EU rules on clinical trials post-Brexit.

Ministers were warned it would be “disastrous” not to adopt the new regulations, which the UK had been instrumental in reforming.

Peers heard that although the regulation had already been agreed, its official introduction had now been delayed until 2020 – after the UK’s split from Brussels.

As such, the Government indicated no firm commitment could be made as it would form part of the divorce talks, but this position was rejected by both supporters and opponents of Brexit in the upper house.