Labour has joined Lib Dem MP Jo Swinson in rejecting the explanation given by Tory chairman Brandon Lewis as to why he breached convention and voted on a key piece of Brexit legislation.
Last night Lewis helped Theresa May narrowly win two crunch votes in the Commons by voting with the government.
However he had been “paired” with Swinson, in the expectation he would not vote in order that she could be at home with her newborn baby.
Lewis and Julian Smith, the Tory Chief Whip, have claimed it was a mistake.
Jeremy Corbyn’s spokesman suggested on Wednesday that Lewis was not being honest about what happened.
“We want a full explanation of what took place. It’s hard to credit the explanation that has been given,” the spokesman said.
“He seems to have been unaware about pairing on the two closest votes. It seems hard to take the existing explanation at face value.”
Swinson herself accused the Conservatives of a “calculated, deliberate breaking of trust”.
Theresa May is under pressure to introduce proxy voting for MPs on parental leave in the wake of the row.
The prime minister said today she was “looking very carefully” at recommendations by Parliament’s Procedure Committee to introduce proxy voting which would allow an MP to cast a ballot on behalf of a colleague.
Normally, all MPs have to vote in person.
Harriet Harman, former acting Labour leader, told May during Prime Minister’s Questions on Wednesday that she must allow MPs to have a vote on the issue.
“Last night’s shambles over the vote of the member for East Dunbartonshire should put it beyond doubt that pairing is not the answer for MPs having babies,” said Harman.
“We are elected as MPs to vote in this House and MPs having babies should not lose that right.”
Harman said it cannot be allowed to happen again, adding: “With more parliamentary babies in the pipeline and more crucial votes coming up it is time to sort this out.
“This one is overdue.”
The prime minister said Lewis and Smith had apologised to Swinson.
“The breaking of the pairing was done in error. It isn’t good enough. It will not be repeated,” she said.
She went on to say she would consider bringing forward a vote.
“We take pairing very seriously and we recognise its value to Parliament.
“We will continue to guarantee a pair for MPs who are currently pregnant or who have a newborn baby,” she added.
She went on to say: “We are looking very carefully at that issue (proxy voting).
“We want to ensure that we can facilitate parental leave in this place but we also obviously have to ensure there is a proper consultation and we are looking at the interests of individuals, but also at the interests of the whole House.”
Orkney and Shetland MP Alistair Carmichael, who secured an urgent question on the matter, later told ministers that events were “symptomatic of a wider problem”.
He said: “It is using a 19th century practice to provide for cover under 21st century employment law and that is no longer good enough.”
The Lib Dem chief whip went on to tell MPs that the situation had improved since he was first elected in 2001, when his son was 10-weeks old, but more needed to be done.
He said: “When I was first elected children were not to be seen and certainly not to be heard within the House.
“I remember I once had to change my younger son’s nappy in the member’s cloak room were obviously he shouldn’t have been because he wasn’t a member on a copy of the Daily Record because there was no changing mats.
“We have come a long way, but anybody who thought that we had done it all and there was no more left to be done was sadly disabused last night.”
Andrea Leadsom, leader of the House of Commons, responded saying the situation that transpired “was not good enough” and again offered an apology on behalf of the Government.
She added: “I’m assured by the Chief Whip that the breaking of the pair yesterday was done entirely in error and will not be repeated.”
Speaker John Bercow said MPs should “decide the issue” when it is debated, adding: “I think there is a concern about potentially an endless debate.”
Shadow Commons leader Valerie Vaz urged the Government to come to an agreement on Wednesday with other parties to “nod through” those MPs on baby leave for every vote.
She added: “We could ensure those voting by this means are denoted with a ‘P’ or, to make it really up to date, and I hope Hansard has this, a baby emoji, therefore giving full transparency to the public.”
Tory MP Heidi Allen urged the Commons to “modernise” before saying: “Dragging in sick and heavily pregnant members does not send a good message to the public - it’s not good enough for us to be OK in here, we have to be better than OK in everything we do.”