An internal Labour report said there was “no doubt” that the union signed up people to Labour to “manipulate” the process in an effort to secure a Westminster seat for its favoured candidate, Karie Murphy.
The report, which was supposed to be confidential, was commissioned by Labour’s ruling National Executive Committee (NEC) to investigate allegations that people had been coerced into signing direct debit forms and Labour membership applications.
The publication of the document led to the Conservative Party claiming that Labour remained in thrall to the trade unions, and the SNP insisting the Scottish Labour leader Johann Lamont had not done enough in response to the allegations.
Ms Murphy stood as a candidate when the sitting MP Eric Joyce was forced out of the party after becoming involved in a brawl in a House of Commons bar. Suspicions of selection rigging emerged when there was a flood of new members of the local Labour Party. A significant number of membership forms were submitted by Unite, led by Len McCluskey.
According to the report, there were 112 members recruited in seven different batches from at least two parties with an interest in selection.
The report concluded that there was evidence members were recruited without their knowledge and that people were pressured into completing direct debit forms. Members were persuaded to supply financial details without being aware they were for completing direct debit mandates.
“There is evidence signatures were forged on either application forms or direct debit mandates or other documents,” the report, published on the Guardian website, said.
An e-mail reproduced by the report indicated that new recruit Lorraine Kane believed that she had been pressurised into joining Labour by Ms Murphy.
In September, Ms Kane clarified her statement in an affidavit suggesting she had never meant to allege any wrongdoing.
It was the controversy over candidate selection in Falkirk that led to party leader Ed Miliband pledging to change Labour’s historic relationship with the trade unions, traditionally the party’s main funders.
Yesterday Labour’s NEC overwhelmingly backed Mr Miliband’s reforms, which will give union members the choice to “opt in” to paying affiliation fees to Labour.
The change – which has to be ratified by a special party conference – would allow those who opt in to party membership to vote in leadership elections. The reforms would see the scrapping of the electoral college system for leadership votes in favour of a one member, one vote system.
Conservative Party 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.”
The SNP MSP for Falkirk West, Michael Matheson, said: “Johann Lamont must take responsibility for the state of her party in Scotland, which is she is supposed to be the leader of. It is time she got a grip of this ongoing fiasco.”
Last night a Labour spokesman said the party was “pleased” that a new candidate for Falkirk – Karen Whitefield – had been “selected through a fair and transparent process”.
The spokesman added: “We are focussed on winning back the people of this area through our positive message of change.”
Labour former chancellor Alistair Darling said the Falkirk row illustrated why Mr Miliband’s plans to reshape the party’s relationship with the unions was vital.
Mr Darling said: “The reforms are absolutely essential.”