Image copyright PA Image caption The revelations come on the day Labour's governing body votes on changes aimed at reducing unions' power over the party

There is "no doubt" the Unite union recruited members to Labour in Falkirk in an effort to "manipulate" the party's selection of a parliamentary candidate, a leaked report says.

The publication of the previously withheld document comes as Labour's ruling body meets to discuss changing the party's relationship with unions.

Ed Miliband wants to change party leadership elections to a one member, one vote system.

Unite called the report a "stitch-up".

Last year the union - the UK's biggest - was accused of trying to rig the selection of the party's parliamentary candidate for Falkirk, to replace the outgoing MP Eric Joyce.

Signatures

The Guardian newspaper has published the full report of Labour's internal inquiryinto the allegations, which up until now had remained secret, with the party saying this was to protect a claimant's anonymity.

Analysis This is a political case study of the law of unintended consequences. It began with a punch-up in a Commons bar involving the Falkirk MP Eric Joyce, who later stood down as a candidate for the next election. And it sparked a chain of events that led to a deep and very public search of the Labour movement's soul. This 21-page report - marked "strictly private and confidential" - offers an insight into the complex, often baffling series of links between Labour and affiliated unions, and the rules that have governed those links. Its publication is an unwelcome reminder for the party of the mess in Falkirk: the claim, the counterclaim, the frustrated investigation, the lack of clear answers. It's a gift for Labour's political opponents.

The 20-page report says "there can no doubt that members were recruited to manipulate party processes" during the selection of a candidate for the next general election.

It finds some union members were signed up without their knowledge and there were some signs membership forms appeared to have been forged.

The report also says there is "evidence that signatures were forged on either application forms or direct debit mandates or other documents".

The investigation was completed last June.

Unite has consistently denied breaking any rules and sources say the full report was full of inaccuracies which the union had no opportunity to rebut.

A Labour spokesman said the party had moved on since the row.

Mr Miliband is also proposing changes aimed at altering the way the leadership is decided.

Labour's governing National Executive Committee meets on Tuesday to discuss his plans for a one member, one vote system.

Trade unionists would no longer be able to vote as a result of their automatic union affiliation, but would have to agree to pay a £3 affiliation fee to Labour to take part.

The key changes A new method of electing Labour's leader - the electoral college, which gives unions, party members and MPs/MEPs a third of the votes each, abolished in favour of one member, one vote MPs have sole nomination rights for leadership candidates and those candidates will need a higher level of support than at present - possibly 15% of MPs All union members will have to 'double opt-in' if they want to take part in a leadership contest. They have to say that they are content to give money to Labour AND that they want to become 'an affiliated supporter' Only full party members - not trade-union 'affiliated supporters' - will choose parliamentary and council candidates Changes to London mayoral selection - Labour's candidate to be selected in the same way as the party leader New leadership rules will be put in place this year - but changes to the party's funding will be phased in over five years

Labour will hold a one-off conference next month to approve the changes.

At the moment, affiliated unions control a third of the votes in Labour leadership elections as part of an electoral college system, last used in 2010 when Mr Miliband was elected.

The proposed changes would give ordinary Labour supporters - as well as party members - more say over who leads them with no individual having more than one vote in a future contest.

Mr Miliband has described his proposals for altering the century-old link between Labour and the unions as "a huge change".

But union leaders have warned of a sharp fall in affiliation fees, with GMB boss Paul Kenny saying the shake-up is not a "done deal".

Speaking to Labour MPs and peers on Monday, Mr Miliband said MPs would need the support of 15% of their colleagues, not 20% as reported in recent days, to put themselves forward in a future leadership election.

He said this threshold would "strike the right balance between protecting the role of MPs and ensuring a diverse range of candidates going forward".

Conservative chairman Grant Shapps said: "As this report shows, Len McCluskey's Unite union was trying to rig Labour's candidate selection in Falkirk.

"Yet Ed Miliband has been too weak to investigate how Unite applied their 'political strategy' in 40 other contests and he even had the publication of this report forced on him.

"Instead, all he has done is give the union barons even more power to buy Labour's policies and pick Labour's leader. Nothing has changed."