Labour’s deputy leader Tom Watson has accused Theresa May of making “blatantly untrue excuses” for the behaviour of her chief whip.
Mr Watson said the PM’s defence of Julian Smith was “unbelievable” and public trust in politics was at stake.
Mr Smith is under fire after telling a Tory MP to take part in a key Brexit vote, despite an agreement not to with a Lib Dem MP on maternity leave.
Pressed on Friday, the PM repeated her claim it was an “honest mistake”
Calls for chief whip who ‘breached trust’ on pairing to resign
Julian Smith openly admitted to a rival chief whip that he intended to break a parliamentary convention in a crucial Brexit vote.
Mr Smith, the Tory chief whip, is facing calls to resign after The Times revealed that he urged three of his MPs to abandon pairing arrangements before the vote on Tuesday night, which the government won by just six votes.
Pairing allows MPs on different sides to agree not to vote so that an absence for illness, travel problems or maternity leave does not count against a member.
The Conservative pairing scandal is another troubling sign for Britain’s democratic norms
For the second time in three weeks, ministers will have misled parliament without facing the consequences.
Pairing is one of parliament’s least understood and most important traditions: as MPs have to be there in person to vote, members of parliament who are sick, on maternity leave, caring for an ill relative, or on ministerial business often miss votes. To avoid changing the outcome through absences, MPs are “paired” with a politician who is going to vote the opposite way, and they stay away from the chamber as well.