Labour has refused to reopen its inquiry into the Falkirk vote-rigging row amid claims that evidence from a key witness was withdrawn without her consent.

A party spokesman said Lorraine Kane had been asked about quotes in the Daily Mail suggesting she had not intended to retract her complaint about alleged irregularities in the candidate selection process.

However, she confirmed that she stood by the sworn statement given to the party's probe in September, according to the spokesman.

"It was that affidavit which was part of the reason that led the Labour Party to conclude there was insufficient evidence to proceed with our inquiry," he said.

"Therefore we have not seen any new evidence to justify further action."

The development came as former chancellor Alistair Darling and Scottish Labour leader Johann Lamont suggested that the issues around the contest in the constituency should be looked at again.

"Something has gone very wrong in Falkirk. There needs to be a very thorough investigation," Mr Darling told the BBC. "I understand the police are looking at matters now.

"If they proceed, then that is what'll happen but if they don't there needs to be a full inquiry and I am quite clear that the results have to be published because that is the only way in which people will be satisfied that justice is done and been seen to be done."

Ms Lamont, speaking on BBC Radio Scotland's Good Morning Scotland programme, said: "I think we certainly need to look at that because obviously there is a concern if the investigation wasn't entirely complete. Again, I say these matters are ongoing. We know that some complaints have been given to the police.

"In this process what we want to do is get beyond the point where people are claiming and counter-claiming and get to the point where again individual Labour party members are treated with respect and, more critically, we fight to get a Labour representative in Falkirk who will stand up properly for the people of Falkirk."

Party leader Ed Miliband has come under pressure to publish a report into the allegations in light of claims that the union ''manipulated'' the process.

The Sunday Times said it had seen emails suggesting the retraction letter of witnesses was written by Unite officials and approved by one of the figures at the heart of the dispute, Falkirk constituency party chairman Stevie Deans, who was also the union's convenor at the Grangemouth petrochemical plant until he resigned last week.

Lorraine and Michael Kane were among those who claimed that they were signed up as members without consent.

Mrs Kane told the Daily Mail: "I did not change the testimony. I did not change anything. I did not withdraw anything. I want all the emails to see what's what. This has been going on for months.

"I don't know what the emails are saying. I want to see everything so I know what was said and if anything was changed from what I said."

But a Labour spokesman said this evening: "Throughout this we have said we will look at any new evidence which might justify the reopening of our inquiry.

"That is why the General Secretary of the Labour Party approached Mrs Lorraine Kane today after reports in the Daily Mail.

"She said today she stands by a sworn affidavit given to us on September 2."

He added: "We have a sworn affidavit and compared it with a short conversation with a journalist.

"It is right to base our decision on a sworn affidavit confirmed again today by Mrs Kane.

"There is now a police inquiry going on into other issues around Falkirk and we will of course consider the outcome of that inquiry."

Unite denies any wrongdoing by members throughout the selection process.

A spokesman for the union said: ''Specifically, Unite entirely denies any involvement in or knowledge of the forging of signatures on application forms or of any documents whatsoever; the coercing of individuals to join the Labour party, however that might be accomplished; the recruitment of individuals to the party without their knowledge or any other breach of Labour party rules.

''Unite called for an independent public inquiry into what happened in Falkirk, and we remain entirely happy to assist such an inquiry, and draw appropriate lessons from it if necessary, should one be established.''

Conservative Party chairman Grant Shapps seized on the intervention by Mr Darling.

"Alistair Darling is the latest senior Labour figure to blow the whistle on Unite's shadowy tricks in Falkirk. Union bosses up there have been pushing Ed Miliband around, fixing Labour seat selections, intimidating families and their young children, and signing up people as Labour Party members without their knowledge," he said.

"Ed Miliband has been totally silent about this ever since he caved in and cancelled Labour's inquiry. If Ed Miliband is too weak to stand up to his union paymasters, then he is too weak to stand up for hardworking people."

A Unite spokesman said: "Unite welcomes the Labour Party statement, which confirms that despite all the bluster in the Daily Mail and the Sunday Times, absolutely nothing new has emerged to contradict or undermine the finding of both the Labour Party and Police Scotland that Unite had broken neither the law nor Labour rules in Falkirk.

"The real scandal is the conduct of elements of the national media, which have shown a willful readiness to disregard any facts which do not fit their anti-union, anti-Labour agenda.

"We appeal to the media to now accept this clarification and leave the people of Falkirk in peace."