Environmental activist Michael Smith yesterday dismissed Fine Gael's condemnation of the Mahon tribunal's investigations into Cherrywood, claiming the party's "self-righteous" words showed them to be "out of their minds".
Mr Smith also said the party's involvement in the development "is an essay in scandal".
He was responding to comments from a Fine Gael spokesman who described the tribunal as "an outrage and a disgrace" for allowing "unfounded allegations" to be made against former Fine Gael minister Seán Barrett, who will be a candidate in next year's general election.
Mr Smith alleged at the tribunal last week that a property developer, the late Phil Monahan, told him in the early 1990s that plans by his company, Monarch Properties, to rezone Cherrywood in south Dublin would go through because he was paying councillors.
Mr Smith, who was involved in the campaign against the Cherrywood development in the early 1990s, claimed that Mr Monahan had told him that Mr Barrett would ensure that his Fine Gael colleagues from outside the area voted for the rezoning.
However, Paul O'Higgins SC, for Mr Barrett, accused Mr Smith of peddling Mr Monahan's malicious rumour to journalists and told him he was a coward for not making the claim in public.
Mr O'Higgins suggested that the boast by Mr Monahan was an effort to discredit Mr Barrett because he had opposed the Cherrywood development at every stage and had spoken out against it. Mr Smith said yesterday he was "very surprised" to find himself "in the same sentence as Fine Gael, Cherrywood and the Mahon tribunal, where the word disgrace is being applied to anybody other than Fine Gael".
He acknowledged that the allegation against Mr Barrett has not been proven.
However, he rejected the claim that he had been "peddling" the story to journalists. "I gave it to journalists to see if they could investigate it - as it was not my place to investigate anything," he said.