The chairman of the Labour Party, Ian Lavery, received £165,000 from the 10-member trade union he ran, a report has said.
Mr Lavery has served as MP for Wansbeck since 2010 and was previously president of the National Union of Mineworkers, succeeding Arthur Scargill.
A report from the Certification Office for Trade Unions and Employers Associations shows Mr Lavery was lent £72,500 to purchase a property from the union's Provident and Benevolent Fund. This loan was written off in 2007 and the report said: "Mr Lavery appears to have been a beneficiary of this arrangement."
It added that Mr Lavery and his wife kept £18,000 from an endowment policy taken out on the property.
The regulator decided not to pursue a further investigation into the issue and Mr Lavery said: "This report should draw a line under almost two years of allegations and innuendo directed at me and my former colleagues."
The report also shows that Mr Lavery received a number of "termination payments" from the union - totalling £89,887.83.
It said: "The allegations further stated that the union's then general secretary Mr Ian Lavery ceased to be general secretary when he was elected as the MP for Wansbeck on 7 May 2010 and questioned in what way this was redundancy and, if not a redundancy, asked on what basis the payments were made.
"The union and Mr Lavery stated that the post of general secretary and therefore, Mr Lavery, were made redundant in May 2010.
"Both the union and Mr Lavery were given the opportunity to provide documentary evidence to show a process or decision by which Mr Lavery was made redundant.
"Neither were able to do so and stated that no such documentary evidence existed
"In light of the absence of documentary evidence to support the union and Mr Lavery's assertions that Mr Lavery was in fact made redundant I do not consider that the appointment of an inspector would help to resolve the key issue as to whether Mr Lavery was made redundant within the terms of his contract of employment."
It was accepted that the union had overpaid Mr Lavery £30,600 in redundancy money, according to the report. Mr Lavery disputed £10,600 of it - and he volunteered to repay £15,000, the report continued.
Labour's shadow international trade secretary Barry Gardiner told BBC Newsnight: "Unions are regulated by the certification officer. Now, your own report says the certification officer has said that there is no reason to make any further investigation, and that no complaint from a member has been made. The industry regulator has said that there is not a case to pursue.
"I know Ian Lavery as a really good man, and as a friend."
Asked if Labour should investigate the matter, Mr Gardiner said: "The Labour Party will obviously want to satisfy itself that no member, we always satisfy ourselves, that no member of the Labour Party brings the party into disrepute."
He added: "You've told us that the proper regulator for the industry has said that there is no further action to take. Now, we will, obviously, satisfy ourselves that all of our members are fit and proper people."
Mr Lavery 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. I am pleased that the certification officer has decided to not appoint an inspector or take further action.
"This report should draw a line under almost two years of allegations and innuendo directed at me and my former colleagues."
The Labour Party declined to comment on the matter.