Former Harper cabinet minister Chuck Strahl is quitting as chief watchdog of Canada's spy agency as the Conservative government seeks to tamp down another ethics controversy before Parliament resumes sitting next week.

While serving as chair of the Security Intelligence Review Committee, Mr. Strahl also registered to lobby the B.C. government over the Northern Gateway pipeline, an energy project that will ultimately require a green light from Ottawa.

The former member of Parliament broke no rules in working for pipeline giant Enbridge but found himself dogged by complaints from NDP and Liberal opponents that someone under hire by the federal government should not be lobbying for a project that requires federal approval.

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The Harper government, which spent much of 2013 scrambling to address criticism over the Senate expenses scandal, has little enthusiasm for defending itself against additional ethical controversies just as Question Period is set to return on Monday.

The Tories must tread carefully in the politics of pipelines. B.C., through which the pipeline would run, has significant misgivings about the Northern Gateway project. The province is home to more than 20 Tory MPs.

Mr. Strahl explained his exit from SIRC Friday by saying that while he had done nothing wrong, he didn't want to figure in a controversy over his actions.

"Despite the fact that my compliance with all relevant rules and regulations has been clearly demonstrated, I retired from politics three years ago and do not wish to be in the centre of the political fray," Mr. Strahl said.

"Nor do I want to be a distraction from the important work SIRC does everyday in ensuring the security of Canadians. It is therefore with regret that I have concluded it is best for all concerned that I step down as chair of SIRC."

Prime Minister Stephen Harper released a statement naming another former Tory MP, Deborah Grey, as interim chair of SIRC. Ms. Grey is already a member of SIRC.

"Mr. Strahl has submitted his resignation to me, and I have accepted it, effective immediately," Mr. Harper said in a statement.

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"With the appointment of Ms. Grey as chair of the Security Intelligence Review Committee, there will be no gap in the review of CSIS's activities or in addressing complaints from the public," Mr. Harper said.

"I would like to extend my personal best wishes to Chuck in all of his future endeavours."

SIRC keeps an eye on the Canadian Security Intelligence Service. The chair's role is a part-time job and a federal appointments website suggests the appointee is entitled to a per diem of between $550 and $650 each day they work.

Mr. Strahl also released a letter from Conflict of Interest and Ethics Commissioner Mary Dawson to demonstrate he had approval to remain in the SIRC post if he had wanted. Ms. Dawson's letter says she does not find him in a conflict of interest over the two jobs and she has no evidence he's contravened rules covering former officer holders.

Mr. Strahl sat as an MP from 1993 to 2011 and served in several posts in Mr. Harper's cabinet, the last of which was transport minister.

NDP House Leader Nathan Cullen heaped scorn on the timing of the resignation – late Friday – and said Mr. Strahl should have known better.

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"A government that's proud of its actions, doesn't make an announcement like this on a Friday evening," Mr. Cullen said.

The NDP MP said a seasoned politician such as Mr. Strahl should have realized the controversy that would be generated by working for SIRC and Enbridge at the same time.

"It should have been common sense that someone with his position, trusted with an important job related to national security, should not be lobbying for a pipeline seeking federal government approval."

The New Democrat called on the Harper government to change the rules so that SIRC members cannot lobby any government.

"Mr. Strahl did the right thing by resigning from SIRC. Now Mr. Harper should do the right thing, close the loopholes on lobbying, and make the appointments to SIRC more transparent and accountable."