Opposition leaders are calling for a public inquiry following new reports about cash payments made to former prime minister Brian Mulroney.

"When you have serious allegations of this kind, you [get] to the bottom of this issue," Liberal Leader Stéphane Dion said in the House of Commons on Thursday.

"It's a matter of democracy. Faced with this information, about Mr. Mulroney, will the prime minister call a public inquiry?"

The call for an inquiry follows German businessman Karlheinz Schreiber's interview with CBC's The Fifth Estate.

Schreiber said there was an attempted coverup to save Mulroney's reputation after he made $300,000 in cash payments to the former prime minister when he was out of office between 1993 and 1994.

Mulroney wanted Schreiber to provide a statement that the former prime minister at no time solicited or received compensation of any kind from the German businessman, Schreiber told The Fifth Estate. But Schreiber did not provide Mulroney with it.

The program also revealed that Mulroney did not pay taxes on the payments in the years he received the money. But Mulroney later made a voluntary disclosure of the income to Revenue Canada.

"Allegations have been raised and they seem sufficiently serious that an inquiry would seem to be the right strategy," NDP Leader Jack Layton said.

Schreiber, who is currently suing Mulroney over the money, has said the payments, handed out in hotel rooms between 1993 and 1994, were intended to enlist his help in establishing an arms factory in Quebec and, later, a pasta business in Ontario.

In 1995, the RCMP investigated allegations that Mulroney accepted kickbacks from Schreiber for the purchase of a large order of Airbus jets when he was still in office.

Mulroney sued for libel over the so-called "Airbus affair," and under oath, denied any dealings with Schreiber.

Mulroney received an apology in 1997

Mulroney received an apology from the Liberal government of former prime minister Jean Chretien and a $2.1-million settlement in 1997.

The Conservative government has said it has no plans to call an inquiry.

House Leader Peter Van Loan pointed out on Thursday that Dion was part of the cabinet that was already forced to pay Mulroney a settlement from taxpayers' money. He said this time, the Liberals can make the accusations themselves, "and pay the price instead of Canadian taxpayers."

A statement Wednesday night from a Mulroney spokesman said The Fifth Estate report was "based essentially on the unreliable and uncorroborated statements of … Schreiber."

It accused The Fifth Estate of conducting a long "vendetta" that is "designed to suggest illegal behaviour by him in relation to the Airbus matter."

As for the tax issue, the Globe and Mail received a letter from an unnamed intermediary of Mulroney's which said the former prime minister was waiting until he was vindicated in his legal battle with the federal government and the RCMP to finalize his tax matters.