Labour is "crying out for leadership" after making a "mess" of its approach in Parliament to the Government's welfare reforms, leadership candidate Andy Burnham has said.
Mr Burnham's comments are likely to be seen as a criticism of interim leader Harriet Harman, who on Monday saw 48 MPs defy her orders to abstain in a key vote on the Government's Welfare Reform and Work Bill.
Unlike fellow leadership contender Jeremy Corbyn, the shadow health secretary did not join the rebellion, saying he was not willing to provoke a "split" in the party.
But he told BBC Radio 4's World at One that the compromise position adopted by Ms Harman "wasn't strong enough for me".
Labour will oppose the Bill "outright" if he is leader when it returns to Parliament in September, he said.
In senior Labour circles there was relief that no shadow ministers joined the revolt - the largest within party ranks since 2013.
But Work and Pensions Secretary Iain Duncan Smith said it made clear Labour was "still the same old anti-worker party – just offering more welfare, more borrowing and more taxes".
Mr Corbyn insisted he was right to oppose the Bill, which imposes many of the £12 billion benefit reductions in Chancellor George Osborne's summer Budget and scraps child poverty targets.
"What I have done, along with 47 other colleagues, is voted against the Government's welfare bill because of the effect it will have on children of large families because of the effect of the benefit cap, particularly in high-rent inner city areas," the left-wing backbencher told Radio 4's Today.
Mr Burnham said it was his intervention which ensured that Ms Harman tabled a "reasoned amendment" expressing Labour's reservations about Mr Osborne's plans, after she had initially told the party's MPs to abstain altogether.
He told the World at One: "It was a mess, wasn't it? The run-up to this vote was a bit of a mess. It is quite clear that this is a party now that is crying out for leadership and that is what I have shown in recent days."
He added: "I persuaded Labour to change its position. It did put down this reasoned amendment. But let me be clear, this was still a compromise position and it wasn't a strong enough position for me.
"I as leader would have opposed this Bill outright last night and would do so if I was elected leader.
"I faced a choice. Having made the party move its position, did I then defy the compromise? I wasn't prepared to split the party and make the job of opposition even harder."
Ms Harman had hoped to use the issue to show that Labour had listened to voters' concerns about the cost of welfare, but the move triggered a furious reaction across the party, with Mr Burnham describing it as "not acceptable".
A Labour Party spokesman played down the rebellion, saying: "Harriet was clear in the position - that we would abstain - and the majority of Labour MPs did so. However, we always knew that there would be a certain number of people who took a different view."
Former Cabinet minister David Blunkett said Labour was suffering "emotional trauma".
"It's bound to be, after the loss in May and the bewilderment about where we go from here," he told Today.
"What we are not doing, of course, is debating enough about where we go from here. So, last night, once again, focused on us being divided rather than what the Tories are doing, a lot of which is unacceptable."