A contender in Labour's botched selection race in Falkirk has broken her silence about the scandal threatening to engulf party leader Ed Miliband.

Linda Gow said there were "serious questions to answer" about why allegations of membership fixing by the Unite trade union had been withdrawn.

She also criticised Tom Watson MP, Labour's former deputy chair, and called for the publication of the original report into the damaging claims.

Labour has been in dispute with Unite for months over the selection of a parliamentary candidate in Falkirk.

The union recruited around 100 new members in a bid to help secure the nomination for its favoured candidate, Karie Murphy.

The two other contenders were communications expert Gregor Poyton and Gow, a local councillor.

The row turned toxic after allegations emerged that some of the new members had been signed up without their consent.

Labour intervened by seizing control of the local party, stopping the new members from voting in the selection contest, and suspending Murphy and Falkirk West chair Stevie Deans.

The report into the allegations has never been published.

Despite the party's tough stance, Labour announced on Friday Murphy and Deans had been cleared, as "key evidence" had been "withdrawn" during the investigation.

Gow, herself a trade union member, told the Sunday Herald she was alarmed by this development.

Gow said: "I have real concerns about the way the original claims were withdrawn. Why would people make claims and then suddenly withdraw them? It doesn't make sense. There are serious questions to answer about this matter."

She added: "It is disappointing nobody has asked why these people have changed their minds. We should see what is in the original report."

On Watson, who raised questions about the allegations, she said: "Tom Watson openly admitted he had not read the report, yet he has taken it upon himself to make claims about the authorship of the letters. The basis for the [original] report was a mess and Ed's office have been able to drill into that issue and realise that."

Eric Joyce, the sitting MP for Falkirk whose conviction for assault last year sparked the selection battle, said the episode reminded him of something "from Sicily".

He added: "It is a great surprise that people who made a formal complaint, verbally and in writing, to the Labour Party of their own volition, have now chosen to withdraw their evidence.

"There are many questions left to be answered."

The episode also raises questions for Miliband, who initially described the Falkirk row as "part of the death throes of the old politics" and symbolic of a "politics that was hated".

The Labour leader used the Falkirk debacle as the basis on which to propose far-reaching reforms of his party's historic link with the unions.

Although Deans and Murphy were cleared last week, a senior Labour source said the new members recruited by Unite would still be unable to vote in the selection contest.

Murphy also confirmed on Friday that she was withdrawing from the race to be the candidate in Falkirk.

Meanwhile, in a sign of the divisions that the row has opened up, two party heavyweights clashed on Twitter about the debacle.

Watson asked shadow Defence Secretary Jim Murphy to apologise for criticising the union, but Murphy declined and aimed a barb in his colleague's direction.

The pair are known to have a poor relationship that goes back to the days of Tony Blair's premiership.

When Labour suspended the two Unite members, Murphy said the union had "well and truly overstepped the mark".

After the pair were reinstated, Watson tweeted that he was sure Murphy "would wish to retract his comments" about Unite.

Murphy shot back: "You know how to get in touch away from Tory twitter eyes m'while I'll just get on with supporting Ed's plans for Party/TU reform."

This was a reference to Miliband's plan to reform his party's relationship with the trade unions, which Watson has expressed doubts about.

In a separate interview, Watson, who has staunchly defended Unite during the row, criticised Labour's handling of the affair, saying: "It's not our finest hour. I've looked at the detail of this since standing down and the problem they had at the start was that the report was flawed, it was inaccurate factually.

"Someone in the Labour Party owes Karie and Stevie Deans an apology. They have had a terrible few months.

"They have been staked out by tabloid journalists, had their characters traduced in the newspapers, been attacked by frontbenchers, and now they've been found innocent of any of the allegations."

Asked if an apology should come from Miliband personally, he added: "It would be a very gracious act if he did."

He also questioned the decision of the party to continue with the centrally led selection process.

He said: "It's unusual, isn't it, that there was no wrongdoing in Falkirk [but] the members are not in full control of their own process."

However, a Labour source insisted that the party would not say sorry to Ms Murphy. "There is no prospect of an apology", said the source.

Instead, Miliband is to use his speech at the TUC conference on Tuesday to insist that the party will not back down on reforming its relations with the unions, despite having to retreat in the Unite row.

He will insist he is "absolutely determined" to press ahead in the face of warnings that more unions will pull the plug financially.

The party leader is to tell the conference: "We need to build a party truly rooted in the lives of all the working people of Britain once more. That is what my reforms are about. It is the right thing to do.

"We have to change. And I am absolutely determined to make this change happen."

Labour's deputy leader Harriet Harman also entered the row yesterday to say: "The outcome of the situation in Falkirk has no bearing on the importance for the future of getting a better relationship between Labour and the trade unions."