Thomas Mulcair was combative from start to finish as he testified in front of a committee of the House to defend the NDP's use of parliamentary funds under Conservative and Liberal questioning.

In a series of testy exchanges, the NDP Leader questioned the legal credentials of Liberal MP and lawyer Dominic LeBlanc, and dismissively referred to Conservative MP Stephen Woodworth as "coco" in French.

Also a lawyer, Mr. Mulcair argued his party had every right to staff "satellite offices" in Montreal, Quebec City and Toronto with taxpayer-funded officials until the rules were changed by his political rivals in April. Pointing to the bylaws of the House of Commons, Mr. Mulcair said parliamentary staff have the right to perform their duties "wherever" they wish, adding nothing prevented them until last month from working in offices where the NDP paid the rent.

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"It was not interdicted prior to that," Mr. Mulcair said. "There is no way that you can apply that retroactively."

Mr. Mulcair did not hide his dislike for the committee probe, stating other party leaders have not had to testify in front of their rivals in such a way. "In my 36 years in government, I've never seen the governing party get together with its handmaiden in the third party to convene the Leader of the Opposition," Mr. Mulcair said.

After he answered a series of questions from Liberal MP Sean Casey, Mr. Mulcair said: "Sorry to destroy your Perry Mason moment, Mr. Casey."

He told Mr. LeBlanc, who has law degrees from the University of New Brunswick and Harvard: "I thought you were a lawyer; maybe I was mistaken."

Mr. Mulcair also engaged in a series of vigorous exchanges with Mr. Woodworth, with the two lawyers lobbing Latin phrases back and forth at one point. Rejecting the arguments of Mr. Woodworth, Mr. Mulcair offered to send him a signed copy of his 1979 book on legal procedure.

"I guess we underestimated the extent to which you are able to make something out of nothing," Mr. Mulcair told Mr. Woodworth.

At another point, Mr. Mulcair told Mr. Woodworth: "I'm giving you a full answer, coco." The term is condescending.

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Mr. Woodworth had started off questioning by asking a series of yes-or-no questions, but the NDP Leader provided long answers, angering Mr. Woodworth.

"Surely I'm entitled to ask questions about what I'm interested in, and not get prevented by the witness rambling on," Mr. Woodworth said.

The controversy goes back to shortly after the 2011 election, when NDP MPs in Quebec pooled their resources to hire staff who could serve their overall communications needs in the province. The staff first worked in Montreal, but new joint NDP offices were then set up in Toronto and Quebec City. There were also plans for an office in Saskatchewan, a province in which the NDP has no MP, but the move was cancelled given the recent controversy.

Conservative MPs said the rules clearly state that staff have to be based either in Parliament or a constituency office. After the committee meeting, Conservative MP Blake Richards accused the NDP of having misused parliamentary funds.

"They must repay the money," he told reporters.

Mr. LeBlanc told reporters that putting parliamentary staff in a party office was wrong, and that the April change to the parliamentary bylaws was akin to an injunction to shut down the NDP satellite offices.

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"I wouldn't find it acceptable that my taxpayers-funded staff would be working in a Liberal Party office in Fredericton … Only Mr. Mulcair seems to think that that respects the rules of the House of Commons," Mr. LeBlanc said.