Belinda Stronach is leaving politics to return to her father's company, as Magna International Inc. considers a bid for troubled auto maker DaimlerChrysler AG.

"It's a critical time for the automotive industry here in Canada and globally, and it's a critical time for the company," the Liberal MP told CTV's Mike Duffy Live.

"The company is facing some major strategic decisions and growth, and I've decided that, at this stage, that's the best role I can play."

Stronach, 40, said she will remain with her party until the next election, when a new Liberal candidate will be chosen to run for her Ontario riding of Newmarket-Aurora.

Several Liberals have chosen not to seek re-election, including former cabinet minister Bill Graham. Stronach emphasized that her decision had nothing to do with Stephane Dion's leadership of the party.

"Absolutely not. It's very simply: this is more about my responsibility to my family and the family business," she said.

"Magna is a huge employer in Newmarket-Aurora and Canada, and I think I can make a greater contribution there at this time.

"I'm one of the few who has served under both leaders -- under Stephen Harper when he was leader of the Opposition, and under Stephane Dion. I can tell you, I think Stephane Dion is the best person to lead this country."

Stronach is expected to serve as executive vice-chair of Magna, one of the top auto parts manufacturers. Her father, Frank Stronach, is Magna's founder and chairman.

CTV's Ottawa bureau chief Robert Fife said he was not surprised by Stronach's decision, noting that she appeared to have become unhappy with her political role.

"She did not have a high-profile critic's role and she had not been prominent in asking questions in question period after Mr. Dion took over," Fife said.

Most recently, Stronach had been serving as Opposition critic for Competitiveness and the New Economy.

Stronach formally entered politics by running for the Conservative party leadership in January 2004. Before then, she was credited with helping to create the Conservative Party, by urging the leaders of the Reform and Progressive Conservatives to unite.

A little more that a year later, in May 2005, Stronach crossed the floor in favour of the Liberals just before a crucial budget vote that could have toppled the Liberals.

Under the leadership of then-prime minister Paul Martin, she became Minister of Human Resources and Skills Development, as well as Minister responsible for Democratic Renewal and Minister responsible for Service Canada.

Stronach's personal life came under the spotlight at the time of her defection, with her public breakup with Conservative MP Peter MacKay.

Stronach later was linked to former Toronto Maple Leaf Tie Domi as the alleged "other woman" in Domi's acrimonious divorce.

In October 2006, MacKay was accused of referring to Stronach as a "dog" during a heated exchange in the House of Commons.

MacKay denied making the comment. After an investigation, House Speaker Peter Milliken said he could find no evidence of the remark and therefore a formal apology was not needed.

"I think she was certainly a political celebrity," Conservative strategist Tim Powers told CTV Newsnet.

Stronach's political mentor, former Ontario premier David Peterson, said the media became obsessed with her personal life, which could be problematic.

"Look, good-looking women get more attention than they probably deserve. But they also get more criticism than they probably deserve," he told The Canadian Press.

"The bad part is everybody's got an opinion on your hair colour and who you're going out with."