OTTAWA - Brian Mulroney is refusing to testify for a second time before the Commons ethics committee about his controversial financial dealings with international arms lobbyist Karlheinz Schreiber.

Through his lawyer, Guy Pratte, the former prime minister "respectfully declined'' the committee's invitation to appear again on Thursday.

In a letter to the committee clerk, Pratte notes that Mulroney provided four hours of testimony to the committee last December, as well as copies of relevant documents. Moreover, he notes that the committee wrapped up its probe into the matter in April and has already filed a report to Parliament.

Hence, Pratte concludes that "no useful purpose would be served by his re-attendance.''

"In any event, the upcoming public inquiry should now be allowed to take its course.''

Opposition members of the committee were not amused. Over the objections of Tory members, they decided last month to resume the committee's probe into the affair precisely because the public inquiry, promised by Prime Minister Stephen Harper six months ago, has yet to materialize.

New Democrat Pat Martin said Mulroney's refusal to make a return appearance is disrespectful and contemptuous of a parliamentary committee.

"The committee has called him to be in attendance on June 12 and that's not optional. That's mandatory.''

Martin said he'll recommend that the committee use its "extraordinary powers'' to compel Mulroney to testify.

However, committee chair Paul Szabo said the committee has already decided that it won't issue a subpoena to a former prime minister.

Szabo suggested the committee might want to pursue other avenues of inquiry and may even choose to sit during the summer if Harper still hasn't named anyone to head up the public inquiry.

"The committee won't look kindly on undue delays and I much suspect, if we don't see some action here, the committee may very well consider reopening our hearings on matters that have not been properly dealt with.''

Among other things, Szabo said the committee might want to hear from Senator Lowell Murray, a former Mulroney minister responsible for economic development in Atlantic Canada.

Murray has revealed that Mulroney asked him to stickhandle a German company's proposal to build a light-armoured vehicle factory in Cape Breton. Unbeknownst to Murray, his work to advance the project helped some of Mulroney's lobbyist friends to earn big commissions from Schreiber, a lobbyist for the German arms manufacturer. The factory was never built.

Martin said he still has plenty of questions for Mulroney himself.

Mulroney has admitted accepting $225,000 in cash-stuffed envelopes from Schreiber to promote German-made light-armoured vehicles abroad.

Schreiber says he gave Mulroney $300,000 and that he was to lobby the Canadian government, potentially putting the former prime minister in violation of federal ethics rules.

Martin said he wants Mulroney to produce evidence, including travel receipts, to back up his "cock and bull story'' about promoting the armoured vehicles in places like China.

"Otherwise, if it looks like a kickback and it smells like a kickback, you shouldn't have to step in it to realize it's a kickback.''