The sponsorship inquiry battle is slated to get more heated this week as two longtime adversaries join the ring to defend their reputations.

Former Prime Minister Jean Chretien, and his longtime rival and successor Prime Minister Paul Martin, are preparing to take their gloves off for the highly anticipated showdown. The two veteran Liberals testify back-to-back, Chretien starting Tuesday and Martin on Thursday.

It will be the first time in Canadian history that prime ministers have ever testified before a public inquiry.

The Gomery Inquiry is seeking answers about how 40 per cent of a $250-million national unity program created by Chretien's government went to advertising agencies that contributed to the Liberal Party.

Chretien will testify Tuesday, CTV's Rosemary Thompson reported.

"He's going to play the Canada card. I'm told he's going to say Canada was at the brink after the referendum in 1995 and that the government had to act and that's why he created the sponsorship program," Thompson reported Sunday.

Meanwhile, Martin is expected to answer questions on Thursday.

"He has said over and over and over again that he did not know about the day-to-day dealings of the sponsorship inquiry that he was really frozen out by the Prime Minister's Office because (he and Chretien) were always at odds over the leadership."

Martin versus Chretien

Despite a long history working for the same party, Martin and Chretien have not had a friendly alliance.

Martin stood beside Chretien as finance minister during the mid-90s. But in June 2002, the tensions boiled over when Chretien, upset with Martin for openly campaigning for leadership, relegated his rival to the backbenches.

Two months later Chretien announced he would be resigning.

Martin scrapped the sponsorship program soon after he became prime minister in December 2003, weeks before Auditor General Sheila Fraser released her report into the program.

Liberal Deputy House Leader Mauril Belanger told CTV's Question Period that he is sure cynicism among Canadians will be tempered by Martin's assurances that they will get to the bottom of the sponsorship scandal.

"This prime minister has said clearly we will find out what happened. He's going to be testifying in this. This is a first," Belanger said.

"We've defended the commission. We've given it every document. We've opened up cabinet documents as well," he said.

Jean Carle, a senior aide to Chretien during his tenure as prime minister, gave shocking testimony at the inquiry earlier last week.

He testified that he helped create a phony paper trail for a deal.

Carle admitted he approved a $125,000 payment to a film producer as a favour so it wouldn't appear on the books of the sponsorship program.

"If this were a drug deal, it would be called money-laundering," Gomery said.

"You're not wrong," Carle said.

But NDP MP Judy Wasylycia-Leis said she would be surprised if the inquiry heard the same sort of testimony from Chretien.

Appearing on Question Period, she added: "It makes it interesting for a commission that may finally be able to get to the bottom of the truth, even though this government keeps putting barriers in the way of access to information and flow of necessary documents."

Belanger disagreed that Carle's testimony was conclusively damning.

"It would be inappropriate to conclude based on one testimony. That's the gist of an inquiry," he said.

"You have to weigh all the items, some of them may be contradictory. Some of them indeed have been contradictory and it is the judge's responsibility to sort through that," he said.

With files from The Canadian Press