By Kevin Krolicki and Bill Rigby

DETROIT/SEATTLE (Reuters) - General Motors Co <GM.UL> has hired Chris Liddell, the chief financial officer of Microsoft Corp <MSFT.O>, as its new finance chief, bringing in a well-regarded auto outsider who could succeed GM's acting CEO Ed Whitacre when he steps aside.

The move, announced on Monday, is the highest-profile hire for GM since it exited bankruptcy in July and completes a whirlwind reshuffling of the top U.S. automaker's senior leadership team under Whitacre this month.

At the end of November, Microsoft said Liddell would be leaving the software maker and was looking at "opportunities that will expand his career beyond being a CFO," leading many to expect he would soon be named CEO of another company.

GM has been operating since July with a new board vetted by the Obama administration and, since the start of December, under acting CEO Whitacre, who had spent a career at telecommunications provider AT&T <T.N> and was already GM's chairman.

Over the past three weeks, Whitacre has shaken up GM's top management ranks by promoting two executives, reassigning two others, and bringing in GM director and investment banker Steve Girsky as his adviser.

GM has begun a search for a permanent CEO although Whitacre has told directors he is prepared to see the automaker through the next stage of its restructuring and possibly through June when it is due to pay off $6.7 billion in U.S. government loans.

As CFO, Liddell will face the challenge of readying GM for a stock offering to reduce the U.S. government's 60 percent stake in the company, and winning back investor trust after accounting missteps, mounting losses, a costly bankruptcy and $50 billion in government aid.

"Being CFO at Microsoft will seem like a breeze compared to what he has to do at GM," said Toan Tran, a Morningstar analyst who has followed Microsoft for several years.

"It's hard to be a bad CFO at Microsoft. You don't have to deal with much when the company generates a billon dollars (in profit) a month."

"GM will be a much bigger challenge," said Tran.

Liddell, 51, a New Zealand native, joined Microsoft in 2005 from International Paper Co <IP.N>, where he was also CFO.

At Microsoft, Liddell was a key player in a range of initiatives that reflected the company's transition to a slower growth business.

Those included Microsoft's first debt offering, a failed bid to acquire Yahoo Inc <YHOO.O>, and a cost-cutting plan set in motion last January that included the biggest job cuts the company had ever seen.