The report will be seized on by Blairites, who are likely to claim Jeremy Corbyn is doing little to address Labour's problems.
Thursday 14 January 2016 22:59, UK
Labour lost the General Election because Ed Miliband was not seen as a potential prime minister and the party was weak on the economy, welfare and immigration.
These are the findings of a review ordered by Harriet Harman after the election, carried out by grandee Margaret Beckett and completed in November, but kept under wraps and now leaked.
The party has said it will publish the review next week, but the leak follows pressure for its publication from Labour moderates led by Dan Jarvis, the ex-Army major tipped as a future party leader.
The conclusions will be seized on by Blairites like Mr Jarvis, who are likely to claim Jeremy Corbyn is doing little to address the failings identified by Dame Margaret, who led the party in 1994 after John Smith's death.
Her report, called Learning the Lessons, includes four key conclusions about why Labour lost the election last May.
:: A failure to shake off the myth that Labour was responsible for the financial crash and failure to build trust in the economy
:: An inability to deal with "issues of connection" and in particular a failure to communicate on benefits and immigration
:: Mr Miliband was judged not to be as strong a leader as David Cameron
:: A fear among voters of the SNP propping up a minority Labour government
Mr Corbyn and his supporters will be delighted that Labour's more left-wing policies - such as the energy price freeze and greater potential to bring railways back into public ownership - were some of the most popular put forward by Mr Miliband.
But Dame Margaret says that despite their popularity there was a lack of a coherent overall narrative.
:: Labour MP Wants Wealth Tax On Party Members
Demanding publication of the report last week, Mr Jarvis told the New Statesman: "Until Labour accepts the lessons of two successive election defeats, we will not renew our politics and reconnect with the public."
After the leak, a party spokesman said: "The formal process of considering the Learning the Lessons report is in its final stages and will conclude next week when it is presented to the relevant committee of the NEC. The Labour Party will then make the report public."
Despite opinion polls showing Labour and the Conservatives roughly neck and neck and pointing to a hung parliament, Labour scored just 30.4% of the vote in the election and won just 232 seats, compared with the Conservatives' 36.9% and 331 seats, and conceded a majority to the Tories for the first time since 1997.
In his only analysis of Labour's defeat so far, Mr Corbyn has said: "We cannot go on being 'Tory-lite' - we've got to be true to ourselves. Labour lost the election because I don't believe we offered a credible alternative to what the Conservatives were offering."
Besides pressure from Mr Jarvis and other Blairites including Chuka Umunna, more than 500 people have now signed a petition calling for the report to be released.
Recommendations in the report include less spin, getting the shadow cabinet to hold meetings outside and the need to have a "simple seamless narrative".
It also calls for a stronger defence of Labour's record in government, declaring: "We should be proud of our record of major social change."
On the financial crash, ruthlessly exploited by the Tories during the election campaign, Dame Margaret's report says Labour should point out how "it paid down debt" before the financial crash.
And it says "we must take the global crash myth head on which dogged us through the last Parliament".
