Mayor Gilles Vaillancourt of Laval, Que., categorically denies all allegations of illegal campaign donations and is threatening to sue his accusers.

Gilles Vaillancourt has served as Laval's mayor since 1989. (Canadian Press)Vaillancourt spoke to reporters Tuesday afternoon, rejecting all stories that have surfaced this week about his offer of illegal donations to Bloc Québécois MP Serge Ménard 17 years ago and Liberal MNA Vincent Auclair in 2002.

"I never tried to give them money. I strongly deny it," said Vaillancourt, his gaze unwavering throughout his news conference.

Vaillancourt also declared his plans to issue legal notice to Ménard and Auclair for a retraction or he "will bring them to court."

The long-serving mayor of Quebec's third-largest city called both men's stories "inexplicable" and suggested they may have a personal agenda against him because he has held power for so long.

Ménard, a former PQ justice minister, went public with his story in an exclusive interview with CBC's French-language service Monday night. He told the network he was offered an envelope containing cash during a 1993 byelection campaign when he was running as a Parti Québécois candidate in a Laval-area riding.

Less than a day after the report aired, Vincent Auclair, a Liberal member of Quebec's national assembly, told reporters he refused an envelope from Vaillancourt while he was running in a byelection in Laval's Vimont riding in 2002.

PQ Leader Pauline Marois has demanded Vaillancourt's resignation.

The province's electoral office is also investigating.

In his television interview, Ménard claims Vaillancourt handed him a white envelope, told him there was $10,000 inside and called it a campaign contribution.

Ménard said he refused the offer and told the mayor he knew the rules: campaign donations can't exceed $3,000 and he could only accept cheques.

The Bloc MP said Vaillancourt seemed upset at the time, turned red and started to tremble, with beads of sweat breaking out on his forehead.

Auclair said he did not look into the envelope offered to him. He said he has been contacted by provincial authorities working with Operation Marteau, a probe investigating corruption allegations in the construction industry, ordered earlier this year by Premier Jean Charest.

Under Quebec's electoral law, convictions for corrupt or illegal practices cannot be imposed after five years have elapsed.