The National Union of Mineworkers (NUM) is to debate its continued funding for a London flat for former president Arthur Scargill, who retired in 2002.
Payments understood to run into tens of thousands of pounds a year have been made for rent and running costs on the apartment in the Barbican since 1982.
A motion calling for an investigation into the allowances is to go before the NUM conference later this month.
Mr Scargill said the union had agreed to make the payments until his death.
The former NUM president said all of his predecessors had been provided with a house bought by the union both during their time in office and in retirement.
"In my case they agreed I should rent a local authority flat during my period in office and following my retirement that would carry on until my death," he told BBC Radio Sheffield.
He dismissed the motion being put to the annual conference in Blackpool on 26 and 27 June as "complete nonsense".
"It is a smear story put about by elements of the NUM who have a different view to me about the direction the union should be going in," he said.
Mr Scargill was given use of the three-bedroom Barbican flat in 1982 when the NUM's headquarters were in London. The union, however, moved its head office to Sheffield the following year.
The motion has been approved for the conference agenda by the union's national executive committee (NEC).
It was tabled by the NUM's Scottish branch and seconded by members in south Wales.
NUM general secretary Chris Kitchen said if the union voted to continue the payments then they would continue, but he wanted to make sure they were approved by members.
"The motion is seeking to revisit whether it is still justified that he [Mr Scargill] should have a property in London paid for by the union for his exclusive use for the rest of his life," said Mr Kitchen.
Mr Scargill said: "Every one of my predecessors has been allowed to remain in their properties following retirement.
"There are many people who have two homes. I have a rented property which I shall cease to have when I die and a property which I bought with my own money in Yorkshire."
Further payments made by the union in respect of Mr Scargill's house in Barnsley, South Yorkshire, have been halted.
Mr Kitchen said he had been sent a letter by Mr Scargill's lawyers demanding those payments were reinstated.
Because they are the subject of legal action, the payments relating to the Barnsley property are not included in the motion to be discussed at the NUM conference.
Mr Kitchen said it was possible Mr Scargill might seek an injunction to prevent any discussion of his expenses at the conference.
"I believe the NEC would want to challenge that," he added.