MONTREAL—Former astronaut Marc Garneau announced his candidacy for the federal Liberal leadership Wednesday, touting himself as a proud patriot who has what it takes to become prime minister.

"Whether it was in the Canadian Navy, as an astronaut or as president of the Canadian Space Agency, I have spent my life serving my country," Garneau said.

"And I am extremely proud of who I am and my contribution to my the country. I believe in commitment and in excellence in everything I do."

Garneau joins a crowded field that includes fellow Montreal MP -- and leadership favourite --Justin Trudeau.

The 63-year-old Garneau was first elected to the House of Commons in 2008 and re-elected in 2011.

The Quebec City native became the first Canadian to fly in space, when he served as a payload specialist aboard the Challenger shuttle in October 1984.

He flew on three shuttle missions, logging over 677 hours in space. Garneau then served as president of the space agency from 2001 to 2005 before jumping into politics.

Garneau's announcement speech was peppered with attacks against Prime Minister Stephen Harper's government.

"Today, I see a Canada that has given me so many opportunities being whittled away," he said.

"Today, under Harper, we have an angry, we have a divisive, we have an intolerant Canada. We have an intolerant government.

"Stephen Harper's government practises the politics of exclusion, the politics of hypocrisy, of deceit. This is a government that rewards the few at the expense of the many."

Garneau is expected to give front-runner Trudeau one of his biggest tests in the race for the top Liberal job.

Garneau, the Liberal house leader, took on the natural resources critic's post last week after David McGuinty resigned.

Defeated in his first run for office in 2006, Garneau was elected in the longtime Liberal stronghold of Westmount-Ville-Marie in 2008.

Garneau adds his name to a packed field of contestants, which includes Trudeau, Vancouver MP Joyce Murray, former Toronto MP Martha Hall Findlay, Ottawa lawyer David Bertschi, Toronto lawyer Deborah Coyne, retired Canadian Forces Lt.-Col. Karen McCrimmon, Vancouver prosecutor Alex Burton and David Merner, former president of the party's B.C. wing.

Toronto lawyer George Takach is expected to join the race on Thursday. Ontario government economist Jonathan Mousley is still hoping to enter if he can raise the stiff, $75,000 entry fee.

So far, only Trudeau and Coyne have officially registered as candidates, filed the required nomination papers and paid the first of three $25,000 instalments on the entry fee.

A number of other potential heavyweight contenders have passed on the contest, including retiring Ontario Premier Dalton McGuinty, former deputy prime minister John Manley, New Brunswick MP Dominic LeBlanc, Halifax MP Geoff Regan and Bank of Canada governor Mark Carney, who will take over as head of the Bank of England next summer.