Labour's acting leader has admitted that a significant number of supporters were relieved when the party lost the election.
Harriet Harman cast doubts over Ed Miliband's economic credibility with the public and said the party had taken the "wrong message" to voters.
Many voters felt the party was failing to reach out to them because it raised issues such as zero-hours contracts, the living wage and food banks, she told T he Independent.
Ms Harman has brought in Gordon Brown's former pollster Deborah Mattinson to give a candid assessment of what went wrong in the run up to the general election.
Mr Miliband's personal performance will be analysed along with the party's lack of economic credibility with voters.
"The two combined together. People tend to like a leader they feel is economically competent," Ms Harman told the newspaper.
Early responses to focus groups staged as part of the inquiry into the humiliating election defeat found relief among some voters that the party had lost.
A supporter in London's Ealing Central and Acton constituency said they were "a little bit disappointed and a little bit relieved", a view that was echoed across the country, according The Independent.
Ms Harman said: "Sometimes after an election, you get a sense that people think 'Oh my God, that is terrible, what a disaster.' That's what a lot of people felt because we got nearly 40,000 new members who were very disappointed.
" But there is an even greater number of people, even though they were not enthusiastic about the Tories, who feel relieved that we are not in government. We have got to address it. It was not a blip."
Labour held six million doorstep conversations with voters but the massive campaign was worth little because it failed to deliver what voters wanted, she told the newspaper.
Ms Harman said a common problem across Britain was that voters felt the party "doesn't talk about me" and it was seen as supporting "people on benefits" but not those who "work hard".
She said: "It doesn't matter how many leaflets you deliver if the message is not right."
Ms Harman said it would be better to have "some turbulence" now than to "paper over the cracks".
"Sometimes after a big general election defeat, some people take lessons that protect their own involvement in the campaign," said Ms Harman.
"They don't want things looked at because they feel defensive. Others want to find things that support what they want the party to do in the future.
"It is really important for the party that it is not defensive about the past but is absolutely honest and clear-eyed and faces up to the truth of what people are saying."