Andy Burnham has insisted that Labour "simply cannot abstain" on the Welfare Bill soon after he abstained in the Commons vote.
The Labour leader candidate took to Facebook to outline his reasons for his actions after nearly 50 of his party's MPs defied interim leader Harriet Harman and voted against the Conservative's Welfare Reform Bill.
He said that he was "firing the starting gun on Labour's opposition" to the reforms and if elected leader would "fight this regressive Bill word by word, line by line".
Tonight I voted for a Labour motion to oppose the Tories’ Welfare Reform Bill.
It was a motion I had been calling for, because I have been clear all along – we cannot simply abstain on a Bill that will penalise working families and increase child poverty.
That’s why last week I took a stand against the Tories’ assault on working families, children and disabled people – and I make no apology for that.
The Tory tax-credit cuts I spoke out against will hit working families who are doing the right thing. They will actually discourage people from being in work.
Children will be hit particularly badly. Many of the measures in this Bill will have the effect of increasing child poverty.
And at the same time as David Cameron is penalising working families, he is choosing to spend hundreds of millions of pounds on an inheritance tax cut for the richest estates.
It speaks volumes about where his priorities really lie.
But whilst we may have lost the vote tonight, that doesn’t mean the battle has to be over.
Labour has been accused of 'disgraceful' behaviour by the SNP over its failure to vote against the Government's Welfare Bill.
More SNP than Labour MPs voted against the Bill which had its first reading in the Commons on Monday, a move which SNP employment spokeswoman Hannah Bardell said Labour would pay the price for at next year's elections to the Scottish parliament.
"Labour had the perfect opportunity to join the SNP in a progressive coalition to oppose the Tories - but with some honourable exceptions they sat on their hands," she said.
"This disgraceful stance will haunt Labour through next year's Scottish Parliament election and far beyond."
Including teller Kelvin Hopkins, the total Labour rebellion stood at 48 of Labour's 232 MPs. The rest of the No votes in the main second reading division were 55 SNP, eight Liberal Democrat, six DUP, three SDLP, three Plaid Cymru and one each from Green and UUP.
The second teller was the SNP's Owen Thompson.
Interim Labour leader Harriet Harman suffered an embarrassing snub in the Commons when nearly 50 MPs defied her orders to abstain over the Government's Welfare Bill.
Some 47 Labour MPs marched into the No lobby against Ms Harman's demand to abstain on the main second reading vote, which the Conservatives won 308 to 124, majority 184. Including a rebel teller, the Labour revolt stood at 48 of the party's 232 MPs.
Three of Labour's leadership candidates, Andy Burnham, Yvette Cooper and Liz Kendall, stayed away but Jeremy Corbyn chose to join the revolt.
London mayor candidates Diane Abbott, Sadiq Khan and David Lammy were also among the rebels. The remaining No votes were made up of SNP and other minor parties.
New post: Tory welfare reform is pure political mischief, but at least 124 of us voted against it http://t.co/tjavNK6Gzt
Ms Harman's reasoned amendment outlining concerns about the Welfare Reform and Work Bill was defeated 308 to 208, majority 100.
The interim Labour leader has insisted her party should not oppose the plans - which cut tax credits, reduce the welfare cap and introduce a "national living wage" - outright because it will not be heard on the issues it has a particular problem with.
Just voted against Tory Welfare Bill. Sorry for colleagues who knew it was wrong but abstained. We weren't sent to Parliament to abstain.
But rebel ringleader Ms Goodman warned the Bill was "obnoxious" and "regressive", highlighting a future limit on tax credits to two children per household as a key failing.
Scottish Nationalist MP Pete Wishart jeered at Labour's disunity over the Welfare Bill vote when he asked the Speaker to move the seating around.
The MP for Perth and North Perthshire raised a point of order requesting the Labour and SNP parties change seats so the Scots could "become the Official Opposition".
Speaker John Bercow wasn't having any of it though.
Rebel leader Helen Goodman has confirmed that 48 Labour MPs voted against sending the Government's Welfare Bill to a second reading.
The former minister tabled a rebel amendment to the Bill but it was not selected for debate and vote despite being signed by more than 50 backbenchers.
However, she and 47 other Labour MPs ignored interim leader Harriet Harman's orders to abstain on the main second reading vote, which the Conservatives won 308 to 124, majority 184.
The government's Welfare Bill - which contains £12 billion of proposed cuts - has been passed to a second reading.
Several Labour MPs - including leadership candidate Jeremy Corbyn and former minister Diane Abbott - voted against the bill, despite the party's official stance being to abstain after an amendment tabled by acting Labour leader Harriet Harman was defeated.
Overall, 308 MPs voted in favour of passing the Bill, while 124 voted against it.
Jeremy Corbyn will be the sole Labour leadership candidate to vote against the government's welfare bill, after Yvette Cooper, Andy Burnham and Liz Kendall stated that they would abstain.
Labour's acting leader Harriet Harman has announced that the party's policy will be to vote in favour of its own amendment to the government's measures, before abstaining on the main vote should the amendment fail.
The Labour amendment opposes some but not all aspects of the Conservatives' proposed £12 billion welfare cuts.
Other Labour MPs are expected to abstain in the vote on the main bill, the details of which were outlined in George Osborne's summer Budget.
Liberal Democrat MPs will vote against the government's proposed £12 billion welfare cuts, new leader Tim Farron has said.
"The truth is the Tories do not have to cut £12 billion from welfare: they are choosing to," Farron said.
He also accused Labour of "silence" on the issue, after stand-in leader Harriet Harman proposed an amendment to the bill, but no plans to oppose it in the main vote.
"The Liberal Democrats will always stand up for families. We will not let the Conservatives, through choice, and the Labour Party, through silence, unpick our welfare system."
The Liberal Democrats' power in parliament was significantly weakened at the last election, with the party's number of MPs falling from 57 to eight.
Andy Burnham, the current frontrunner for the Labour leadership, has said he will abstain from today's main vote on the government's welfare plans if a Labour amendment does not pass.
Some Labour figures could vote against the measures in parliament tonight - directly undermining acting leader Harriet Harman's call for the party to abstain.
The bill - outlined in George Osborne's Budget - will include measures to cut the welfare cap and restrict tax credits to two children per family.
Burnham, along with fellow leadership candidates Jeremy Corbyn and Yvette Cooper, opposed Harman's original plan not to oppose the plans - with Harman then tabling an amendment seeking to block the government's proposals.
"The Tories want to use this period to brand us in the way they did in 2010. We must not allow that to happen," he said in an open letter to colleagues.
"Collective responsibility is important and it is what I would expect as leader of our party. It is why I will be voting for our Reasoned Amendment and, if it is defeated, abstaining on the bill."
However, he added that the move would be "only the beginning of a major fight with the Tories over the measures, adding: "I am determined that we will fight this regressive Bill line by line, word by word in committee. If the Government do not make the major changes during committee stage, then, as Leader, I will oppose this Bill at third reading."
Labour's interim leader Harriet Harman faces a potential revolt by the party's MPs in today's Commons vote on the government's welfare bill.Read the full story ›