Prime Minister Stephen Harper announces on Friday that Helena Guergis has resigned from cabinet. (Adrian Wyld/Canadian Press)

Prime Minister Stephen Harper has asked former cabinet minister Helena Guergis to sit outside the Conservative caucus while the RCMP investigates "serious" allegations over her conduct.

In an email sent Friday before the prime minister held a news conference in Ottawa, Guergis announced she had resigned as minister of state for the status of women, ending her tumultuous tenure in Harper's cabinet.

Helena Guergis speaks during question period in the House of Commons earlier this month. (Sean Kilpatrick/Canadian Press)

Harper said he learned of the allegations against Guergis on Thursday night and immediately referred them to the Mounties, as well as the commissioners for ethics and conflict of interest. In the meantime, he has asked Public Works Minister Rona Ambrose to assume Guergis's cabinet responsibilities.

"Those allegations had to do with Ms. Guergis's conduct and do not involve any other minister, member of Parliament, or federal government employee," Harper told reporters outside the Commons, without providing more details about the allegations.

"Ms. Guergis offered her resignation from the ministry, and I accepted it. Pending a resolution, she will sit outside of the Conservative party caucus."

Allegations 'peripheral' to Jaffer dinner

Speculation over when the unpopular junior minister's time in cabinet would come to an end escalated mid-week after media reports about the alleged business dealings of Guergis's husband, former Alberta Tory MP Rahim Jaffer.

A Toronto Star report on Thursday alleged Jaffer boasted to potential clients about his connections inside the Prime Minister's Office at a liquor-filled dinner meeting in downtown Toronto last September. Later the same night, while driving home, he was arrested on charges of impaired driving and cocaine possession. The PMO dismissed Jaffer's alleged claims of influence as "false" and "absurd."

It also emerged Thursday that Jaffer was using a parliamentary email account through a wireless device given to him by Guergis.

Sources told CBC News that the prime minister received the "credible" allegations against Guergis late Thursday night. The sources said Guergis did not volunteer any information herself, as Harper didn't speak to her until Friday morning.

The sources added the allegations are "peripheral" to Jaffer and not directly linked to the alleged events of the dinner meeting reported in the Star story.

CTV News reported Friday night that the RCMP is investigating whether Jaffer used his wife's parliamentary office for private, commercial business and whether Guergis accompanied him to business meetings.

Remains MP for Simcoe-Grey

Guergis has faced repeated calls for her resignation after she apologized for throwing a tantrum in Charlottetown Airport in February, during which she allegedly swore at airport staff and referred to the city as a "hellhole." This week, the Liberals asked the federal ethics commissioner to probe the financing of her purchase of an Ottawa home.

Jaffer, who represented the Alberta riding of Edmonton-Strathcona — first as a Reform Party MP and later as a Conservative — pleaded guilty to a charge of careless driving stemming from his Sept. 10 arrest and was ordered to pay a $500 fine, but the more serious charges against him were dropped.

In her email announcing her resignation, Guergis said she will remain the MP for the southern Ontario riding of Simcoe-Grey. She said the past nine months have been a "very difficult time" for her.

She apologized again for her "emotional" behaviour in February and insisted she would never insult Prince Edward Island, her father’s birthplace.

"I have worked hard for Canadian women, and I am proud of my record of my accomplishments on their behalf," she added.

PM must 'be straight': Ignatieff

Liberal Leader Michael Ignatieff said the prime minister must restore public confidence in the government and Parliament by coming clean about the whole affair.

"He's got to come out and level and be clear and be straight and then I think we all want to move on," Ignatieff told reporters on Friday outside the House. Ignatieff said it’s not credible for the government to say MPs had no contact with Jaffer, a former MP, who was using the Conservative logo on his website until Thursday.

"There are a huge number of questions to which Canadians need an answer, and the idea that this is over seems to me mistaken," he said. "It’s continuing because this government cannot level with the Canadian people."

NDP Leader Jack Layton said Harper should reveal to the public the allegations against Guergis.

"I think he would be obliged. He said he would run the most transparent and open government that we had seen," Layton said. "But let’s face it, that’s not happening and Mr. Harper’s tendency is to be very closed about things. You get the impression he was dragged kicking and screaming into this one."

Guergis was first elected to the House of Commons in 2004. She served as parliamentary secretary to then trade minister David Emerson after the Conservatives were elected to form a minority government in 2006.

In 2007, she was promoted to secretary of state for foreign affairs and international trade, and secretary of state for sport. She was named minister of state for the status of women following the 2008 federal election, which saw Jaffer defeated in his riding. The two married the day after the election.