Labour will not contest the Government's latest round of welfare cuts, including the lower household benefits cap and new limits on child tax credits, the party's acting leader has said.
Harriet Harman told the BBC that her party had to acknowledge that it lost the election because voters did not trust it "on the economy and on benefits".
Ms Harman said Labour would oppose some of the changes to tax credits, as well as the abolition of the child poverty targets, but that they wouldn't do "blanket opposition" because people don't want it.
Left-wing Labour leadership contender Jeremy Corbyn indicated he would not support Ms Harman's decision.
"If it is proposed that Labour MPs are being asked to vote for the government's plans to cut benefits to families I am not willing to vote for policies that will push more children in to poverty," he said.
David Cameron was told to "show more class" and answer the questions by Harriet Harman during a heated Prime Minister's Questions today.Read the full story ›
Harriet Harman has rejected the proposal that a new Labour leader should be put up for re-election in three years' time.
Some Labour MPs, including shadow education secretary Tristram Hunt, have suggested the next leader have a "test run" and seek re-election or re-endorsement before 2020.
But Harman, who is acting leader of the party, told The Observer whoever is elected should be allowed to get on with the job for the next five years.
Harman also announced a "truth and reconciliation" commission to discover why Labour lost the General Election.
The Labour Party wants to hold televised hustings in the parts of the country where it lost when it elects a new leader over the summer.
Interim leader Harriet Harman said she hoped to arrange "robust, tough, televised hustings which involve the public", and that she was speaking to broadcasters to make it happen.
She said: "Last time our hustings - in front of Labour members - were in cities where Labour won. We must have those hustings now in towns and suburbs where Labour lost.
"We have to go back and ask local people from those areas to be brutally honest about what they think of us and what they want from us."
Labour's interim leader Harriet Harman has said she wants to "let the public in" on the party's forthcoming leadership election.
Therefore, she has announced that anyone who pays the £3 fee to register as a Labour supporter will get a vote in the election.
She said: "Anyone – providing they are on the electoral register – can become a registered supporter, pay £3 and have a vote to decide our next leader."
She said the party had asked itself the wrong questions, deciding "who do we like" rather than "who does the country like" in previous contests.
Harriet Harman has admitted that the shock exit poll published at 10pm on election day was "a body blow none of us will ever forget".
Labour's interim leader made the remark in a speech on the party's forthcoming leadership contest.
Acting Leader of the Labour Party, Harriet Harman, paid tribute to Jim Murphy after he stood down as leader of the Scottish Labour party, saying he "has been a hugely important figure."
Jim has given so much to the Labour Party over the last twenty years. He, I know reluctantly, took the responsibility for leading Scottish Labour at the most difficult election they have ever faced. He did so with incredible energy, purpose and dignity.
As a cabinet minister and leader of his party in Scotland, Jim has been a hugely important figure in the Labour Party. He leaves with the best wishes and thanks of our movement.
It will now be for the Scottish Labour Party to choose its next leader.
Harriet Harman is stepping down as Labour's deputy leader, she has announced.
She paid tribute to Ed Miliband "for his leadership" and "for his decency, his commitment and his constant striving for a fairer country".
In a speech, she said: "On the resignation of Ed Miliband as leader of the Labour Party I, as his deputy, am stepping forward to be acting leader until a new leader is elected by the party."
She added: "With a new leadership team in place, after what has undoubtedly been a serious defeat, the Labour Party will be best placed to be the strong opposition this country needs - defending our NHS and our public services, and fighting for fairness, equality and social justice.
"That determination will be all the fiercer in the face of this Tory government."
Labour's deputy leader Harriet Harman has questioned whether the Conservatives could form a majority government with any other party.
Harman urged people to treat an exit poll, predicting the Tories would be the largest party, with caution, saying there were many seats which were going to be "very close".
She told ITV News: "If the exit poll is right...what it shows is the coalition led by David Cameron has more or less lost its majority.
"We'll have to see whether the new House of Commons that's been newly elected will give David Cameron a majority."
"I think it's far too early to say."