Falkirk vote-rigging claims: Jack Straw calls for new inquiry
Former cabinet minister Jack Straw has said the party should "actively consider" reopening its investigation into the Falkirk selection process.
On BBC2's Daily Politics, the Labour MP said there was "a sufficient case... for there to be further questions that will need to be dealt with".
The Sunday Times newspaper has reported that Unite thwarted the party's initial investigation.
The union was accused of rigging the selection of a parliamentary candidate.
It denied doing "anything untoward" during Labour's internal investigation.
The affair began when Falkirk MP Eric Joyce announced he would be stepping down at the next general election in 2015 after he was convicted of assault at a House of Commons bar.
Labour investigated allegations earlier in 2013 that Unite had tried to sign up members without their knowledge in the constituency so that the union's favoured candidate was chosen to contest the 2015 general election for Labour.
The investigation cleared Unite and its members of any wrongdoing after key witnesses withdrew their allegations, but the Sunday Times said it had seen a cache of emails raising questions about whether Unite influenced the outcome of the inquiry.
Mr Straw said: "I don't think this is going to go away."
Falkirk MP Eric Joyce said Labour was protecting the Unite organiser at the centre of a selection row because it "fears" the organisation's leadership.
Unite official Stevie Deans, who had worked at the Grangemouth petrochemical plant for about 25 years, resigned on Monday.
He had been suspended by owner Ineos over claims he had used company time for political campaigning work.
Ineos had been expected to reveal the outcome of a disciplinary case against him on Tuesday.
The union previously voted for strike action over his treatment, which led to last week's shutdown of the plant.
Separately, Mr Deans was accused of being involved in the Falkirk vote-rigging claims.
He was suspended from the Labour Party but was later cleared by an investigation and reinstated.
Former Foreign Secretary Mr Straw, the Labour MP for Blackburn, said the union had adopted "catastrophic tactics" in the industrial dispute at Grangemouth.
"Whichever way you look at what happened at Grangemouth it's hard to see how on earth the Unite union ended up with those tactics," he continued.
"Is there something of concern there? Of course there is. And is it a saga that does not reflect well on the national leadership of Unite - both in respect of their relations with the Labour Party but also in respect of their representation of their members at a huge plant like Grangemouth? Yes."
Unite chief of staff Andrew Murray told BBC Radio 4's Today programme: "Neither Unite nor anyone working for Unite made any contact with any witness to the Falkirk inquiry at all.
"All the statements that were sent in were agreed, approved and signed to the best of my knowledge by the people who signed them.
"There is no evidence even in the emails that have been printed by the Sunday Times that Mr Deans did anything untoward at all."