Chief whip faces calls to quit after he is accused of lying over critical Brexit vote

The Chief Whip is facing mounting criticism from Tory colleagues and calls to resign after it emerged that he urged Tory MPs to break with "pairing arrangements" to avert a damaging Brexit defeat.

​Julian Smith was accused of lying after he asked Tory MPs to break parliamentary convention under which pairs of MPs on different sides of the house agree not to vote so an absence for illness, travel or maternity leave does not affect the result.

Brandon Lewis, the Chairman of the Conservative Party, voted on a key vote on the customs union on Tuesday after being told to break his pair by Mr Smith.

It breached a deal with Jo Swinson, a Liberal Democrat MP who is on maternity leave, who accused him of "cheating". Mr Lewis has apologised to Ms Swinson and insisted it was an "honest mistake" by whips. The Prime Minister also claimed on Wednesday that the pairing breach by Mr Lewis was "in error".

However, doubt was cast on their version of events on Thursday after Westminster sources said Mr Smith told Alistair Carmichael, the Liberal Democrat chief whip, that he had deliberately intended to break the pairing involving Mr Lewis.

But he added that he had been unaware that his pairing involved Ms Swinson, and MP on maternity leave, and apologised to Mr Carmichael.​

Four other Tory MPs said that they were told to break their pairs but refused to do so. One told The Sun: "Julian told me I was needed and told me to come in and vote. Of course he knew I was paired. I didn't vote and honoured my pair, and he demanded to know why not afterwards. It then appears Julian told the Prime Minister it was all an honest mistake."

The Conservatives won the vote, which would have forced the Government to make staying in the Customs Union an objective of negotiations, by just six votes.

Heidi Allen, a pro-European Tory MP, said: "I sincerely hope this isn’t true. No matter how tough the going gets, principle, integrity and standards matter. Without those, what’s left?”

She added last night: "I regret to inform that despite repeatedly asking Julian Smith direct questions this afternoon, he has been unable to confirm to me that he did not give instructions to break pairs. Therefore I can only conclude MPs were told to break pairs on Tuesday.

"When I became an MP in 2015, I was determined to challenge stereotypes about politicians. I refuse to be tarnished by this behaviour so will not stand by and say nothing. Integrity and honesty are fundamental to our democracy. Anything less is unacceptable."

Peter Bone, a Eurosceptic Tory MP, said that the Commons ran on "tradition and trust" and he would be "very concerned" if pairing arrangements had broken down.

Ian Lavery MP, chairman of the Labour Party, said: “The Tories’ story is changing by the minute as they desperately scramble to cover up their appalling actions. This government is rotten to its core. Julian Smith and Brandon Lewis must now resign or be sacked, and Theresa May must apologise for misleading the House.”

Tom Watson, the Deputy Leader of the Labour Party, said: " Someone is lying here. Either the Chief Whip resigns or the Prime Minister is tainted by his disgrace."

A Conservative spokesman said: “We have apologised for the fact that a pregnancy pairing arrangement was broken in error this week. No other pairs offered on the trade bill on Tuesday were broken.”