Marc Mayrand, Canada's chief electoral officer, weathered a barrage of questions Wednesday from Tory MPs on the House of Commons ethics committee. (Fred Chartrand/Canadian Press)

Opposition members of the federal ethics committee agreed Wednesday on 78 witnesses they want to question as part of a probe of Tory election ad spending, a list that excluded names suggested by Conservative committee members.

Opposition members said the fuming Conservatives' proposed witnesses are irrelevant to the investigation because they are from other parties and weren't involved in the Tories' 2006 election campaign.

The House of Commons ethics committee is probing allegations that the Tories overstepped legal limits on election advertising spending by disguising the cost of national ads as local expenses.

Tory members argued that their witnesses would show that other parties make similar financial transactions during elections, as a second day of hearings into the affair degenerated into partisan bickering.

"You should be ashamed of yourself," Conservative MP Scott Reid shouted at committee chair Paul Szabo, a Liberal, after being cut off in mid-sentence.

"You're a disgrace to this Parliament, Paul Szabo, just a disgrace."

Reid and other Conservative MPs complained throughout the day as Szabo strictly applied House of Commons rules.

They also continued to ask Canada's chief electoral officer, who appeared before the committee for a second day Wednesday, why he is investigating their party and not others over spending during the 2006 general election.

Tory committee members suggested that Elections Canada head Marc Mayrand's replies were evasive and that he was using their party's ongoing lawsuit against his office and a federal investigation into their finances as pretexts for withholding answers.

Elections Canada is looking into $1.3 million in Conservative party ad spending that the federal agency alleges was illegally channelled via the campaigns of local candidates during the 2006 election.

The Tories, who are suing Elections Canada over the matter, say all parties used the same techniques to move money between national and local campaigns. Conservative MPs at Wednesday's hearings in Ottawa repeated assertions that the Bloc Québécois had openly used the funding scheme in the past and demanded to know why Mayrand didn't investigate that party.

Mayrand said he was reticent to discuss matters already before the courts, fearing it might compromise legal proceedings.

When Szabo asked whether he wanted to sum up his testimony, Mayrand said only: "I would simply reiterate to the committee that I am here to serve Parliament, impartially, fairly and for all parties and candidates."

Mayrand's responses prompted outraged responses from several Conservative committee members.

"That's not the way we do things," said Ontario MP David Tilson. "I say, if we're going to continue on with this hearing, we be allowed to ask any question that we wish."

Szabo called a 'blabbermouth'

Tilson and his caucus colleagues flooded the committee with points of order, prompting Szabo to shut down the hearings at one point.

One Conservative called Szabo a "blabbermouth" but later apologized. Another described the hearing as a "Liberal PR stunt."

NDP committee member Pat Martin said the Tory attacks on Mayrand were worrisome.

"We're on a dangerous and slippery slope when the government of Canada expresses non-confidence in the chief election officer," Martin said.

The day before, Mayrand told MPs he had asked Elections Canada staff to review the returns of all major political parties in the 2004 and 2006 federal elections.

The review, he said, found no evidence that other parties had employed the so-called "in-and-out" money transfer scheme that the Tories are alleged to have used.

With files from the Canadian Press