Labour leadership contender Aodhán Ó Ríordáin, who is leading the campaign against housing development at St Anne's Park in Dublin, proposed planning changes to allow residential development on the land.
Mr Ó Ríordáin was a member of Dublin City Council in 2005 when he and his colleagues called for residential development use on Z15-zoned, institutional lands. This includes the St Anne's site in Raheny.
However, in recent years he has spearheaded opposition to plans by Pat Crean's Marlet Group to develop on St Paul's College land.
Mr Ó Ríordáin and local campaigners hope for a judicial review against An Bord Pleanála's decision last month to allow more than 650 homes there.
Last week, Marlet wrote to Mr Ó Ríordáin claiming his role in rezoning Z15 lands to include residential use "appears significant".
The letter, signed by Mr Crean, claimed the newly-elected TD's involvement appeared to be "entirely at odds" with, and "makes a mockery of," his position as an opponent of the development.
Minutes from a council meeting held on January 31, 2005, show a motion by Labour Party councillors, including Mr Ó Ríordáin, calling for residential development to be allowed on Z15 sites.
It was a proposal that received cross-party support and the Labour motion was ultimately withdrawn.
Last night Mr Ó Ríordáin told the Irish Independent that he did not represent the area at the time and hit out at the developer for "playing the man not the ball".
"I received a bizarre correspondence from the developer over the weekend. I consider it quite inappropriate. The democratic process is there for people to engage with it," he said.
"I support the democratic process, I don't trust developers.
"He is in it for profit, that's the capitalist society we live in, I'm not in it for any profit."
Asked about his motion to allow residential development on the land, he said Z15 zoning is "clearly for institutional use", such as by a religious order.