Mr Miliband suspended the selection process in the Falkirk seat following allegations that Britain’s biggest trade union had packed the local constituency party with its supporters, to get its candidate chosen.
But last month, the Labour leader was forced to back down, after local activists withdrew their complaints.
Now new evidence allegedly suggests that the retraction letter was written by Unite officials and approved by one of the figures at the heart of the Grangemouth dispute, Falkirk constituency party chairman Stephen Deans, who is also the union’s convener at the plant. The e-mails have been passed to police in Scotland, who earlier ruled out an inquiry – and there will now be fresh pressure on Labour to reopen its own investigation.
Scottish Labour leader Johann Lamont said yesterday: “I haven’t seen the e-mails, but obviously if there are serious allegations they do need to be looked at.
“What I am very determined and focused on is making sure in the next period, we’re concentrating on getting an open process for selection and getting a candidate who will represent Labour.”
Peter Watt, the party’s former general secretary, said: “Understandably the initial inquiry was pulled because of lack of evidence. If new information has surfaced that puts a question mark over that lack of evidence, the party should consider re-opening its inquiry.” The revelations were unearthed by bosses at Ineos, the company that runs the Grangemouth oil refinery complex, which was brought to the brink of closure in a row with Unite last week.
Lawyers acting for the firm allegedly discovered that Mr Deans, who is also the constituency party chairman in Falkirk, had been using his work e-mail address for political correspondence.
An Ineos spokesman said Mr Deans was last week presented with the findings of its inquiry into the alleged “inappropriate use of company resources and systems”.
The firm will make a further announcement tomorrow.
The findings of the inquiry reportedly included a draft of the party activists’ retraction letter, which was sent to Mr Deans for him to get it signed by Michael and Lorraine Kane.
They were witnesses who had initially complained to the party against Mr Deans and Karie Murphy – Unite’s choice to become Labour’s prospective parliamentary candidate in Falkirk after MP Eric Joyce announced he would not stand again following his arrest in a House of Commons bar brawl.
Mr Deans and Ms Murphy were suspended by Labour when the inquiry was launched, but charges against them were dropped and they were reinstated as members after the Kanes withdrew their complaint.
Police Scotland was initially called in by Labour when allegations of irregularities emerged in July, but determined that there was not enough evidence of wrongdoing to launch an investigation.
The new cache of e-mails has now been handed over to the force.
A Police Scotland spokeswoman said: “Information was handed in to Falkirk police on Friday and this information will be looked at by police.”
Unite denied any inappropriate contact with witnesses.
“Unite was the subject of entirely unjustified attacks in relation to the Labour parliamentary selection in Falkirk,” a spokesman said. “Both the Labour Party and Police Scotland investigated the issue and found that neither the law nor the party’s rules were broken by the union.
“The e-mail exchanges, apparently leaked by an employer for its own purposes, do nothing to change that.”
The trade union carried out its own investigation into the Falkirk episode, but had no “direct contact” with anyone involved in the Labour Party investigation.
The union spokesman added: “It is normal for people subject to investigations which at one time involved the police to avail themselves of legal assistance in preparing their responses.
“It is also normal for Mr Deans to have dealt with the Kanes, who are members of his family, and further normal for Unite to provide assistance to its members who had done nothing more dangerous than try to involve themselves in democratic public life.
“This continuing media witch-hunt demonstrates how threatening some elements in society continue to find such involvement by working people.”
Conservative Party chairman Grant Shapps also called for Labour to “immediately” reopen its Falkirk inquiry.
“These e-mails confirm that Unite planned to infiltrate the Falkirk Labour Party to ensure their candidate was selected and, when the inquiry was opened, went so far as to write the statements from key witnesses withdrawing their evidence,” claimed Mr Shapps.
“Ed Miliband failed to stand up to the unions in Falkirk and backed down in the face of pressure from [Unite general secretary] Len McCluskey. If he is too weak to stand up to his union bosses and tackle what he himself called ‘bad practices’, how can he stand up for hard-working people?”