A key ally of Jeremy Corbyn who is fronting a campaign about justice for miners is under fire over why their union paid him £165,000, partly because he left to become an MP.

Ian Lavery was told the money would have been “better spent on miners’ welfare”, when confronted on the campaign trail by a reporter.

“Why do you need to have redundancy just when you switch from being a union official?” the Labour party chairman was asked.

But Mr Lavery refused to answer questions about the controversy, which saw him lent £72,500 for a house from the Northumberland branch of the National Union of Mineworkers (NUM) when he was branch general secretary.

The loan was written off 13 years later and the shadow cabinet member also received nearly £90,000 in “termination payments” from the union when he left to stand as an MP in 2010.

Although he volunteered to repay £15,000, a regulator’s report found this was less than the £30,600 the union believed it had overpaid.

The episode is receiving fresh attention after Mr Lavery appeared in a video vowing to “bring justice to mineworkers” and accusing the Conservatives of stealing the miners’ pension fund.

“Haven’t you got a bit of cheek doing that when you received £165,000 or so from the NUM for redundancy and for paying off your mortgage,” asked Michael Crick, the veteran political reporter.

“I wouldn’t expect to get a redundancy payment when I move from doing one job to another. Couldn’t that money have been better spent on miners’ welfare?”

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But Mr Lavery, who is defending the seat of Wansbeck, in Northumberland, turned on Mr Crick and accused him of trying to “interrogate” him.

“What’s your wages?” he asked, also attacking the reporter for “making things personal” and telling him to “be grown up about things”.

“Can we get onto something which is really serious with regard to the mineworkers’ pension scheme” Mr Lavery said.

The 2017 report, by the Certification Office for Trade Unions and Employers' Associations, said the original loan made to Mr Lavery, in 1994, was at below market rate.

It was written off 13 years later when an endowment policy taken out against it failed to perform as expected. Mr Lavery and his wife kept £18,000 from the endowment policy, the report found.

When it was published, the MP said: “Under my stewardship the union always complied with the rules and the certification officer signed off every year's transactions.

"As the certification officer's report makes clear, no member of the union, past or present, has made a complaint about the financial affairs of the union.