Correspondence with Prime Minister Stephen Harper shows Mulcair opposed appointing former MP Deborah Grey due to her lack of experience with intelligence issues. He also feared the possibility of conflict of interest in the case of Gene McLean, a former security consultant.
In a third case, Mulcair found lawyer Yves Fortier's inexperience with security intelligence "cause for some concern," but he ultimately did not object to the appointment given Fortier's reputation as one of Canada's foremost commercial law experts.
The NDP released copies of the three letters to The Canadian Press.
The party has chastised the government for leaving two other chairs on the watchdog committee empty at a time when the government is looking to bolster the powers of the Canadian Security Intelligence Service.
The Conservative government has repeatedly expressed confidence in the committee's ability to fulfil its role.
The committee was left as the only watchdog keeping an eye on CSIS when the government abolished the inspector general's office.
Two successive committee chairmen — Dr. Arthur Porter and Chuck Strahl — resigned amid questions about their private business dealings. Grey became interim chairwoman earlier this year following Strahl's departure.
Porter, jailed in Panama, is fighting extradition to Canada, where he is wanted for his alleged role in a multimillion-dollar contracting conspiracy.
The law governing CSIS says appointments to the review committee, known as SIRC, are to be made after consultation by the prime minister with leaders of the official Opposition and any party with at least twelve seats. However, it does not include explicit veto powers.
In an April 2013 letter to Harper, Mulcair praised Grey as an accomplished Canadian who had given back to her community generously.
"However, I believe SIRC necessitates a nominee that is abreast of today’s security intelligence environment and, preferably, steeped in Canadian and International Law. Mrs. Grey’s wealth of experience and training unfortunately fail to meet these requirements," Mulcair wrote.
"If the experience of Dr. Porter has taught us nothing else, it’s that any further appointments to SIRC must have unqualified credentials to support SIRC’s mandate and to reaffirm Canadians faith in this institution."
In a March 2014 letter about McLean, the NDP leader said he didn't "believe it is appropriate to nominate him without measures being taken to deal with any possible conflict of interest."
"If you have further assurances regarding this possible conflict of interest, I would be pleased to hear them in order to be able to positively respond to this nomination."
An NDP spokesman said he was unaware of any responses from the government concerning the three nominees.
A civil liberties group recently objected to Fortier heading up a review committee investigation of alleged spying on environmental activists, citing a conflict due to his former petroleum industry ties.
The British Columbia Civil Liberties Association asked that Fortier recuse himself since he once sat on the board of TransCanada Pipelines — the company behind the Keystone XL project.
In a recent interview, Grey said the matter was "working its way through the proper channels to see if he will continue to hear that case."
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