NDP Leader Jack Layton stunned Canada's political arena on Monday, announcing he is taking a temporary leave of absence to receive treatment after doctors discovered he has a new cancer.

The surprise announcement comes just over two months after Layton led his party to record gains in the federal election and Official Opposition status in the House of Commons.

Layton, speaking at times with a strained voice alongside his wife, NDP MP Olivia Chow, vowed to return to his position when Parliament resumes on Sept. 19.

"I will beat this new cancer and I will be back in the House of Commons to defend the values and priorities of Canadian families," he told reporters at a news conference in Toronto.

Layton's departure, however long, creates a significant problem for the New Democrats, who have faced repeated questions about the experience levels of some of their new MPs in opposition to Prime Minister Stephen Harper's Conservative majority government.

Layton is considered the most popular federal leader among Canadians and is largely credited with his party's unprecedented success in May's general election, which saw the New Democrats become the second-largest party in the Commons, the Bloc Québécois decimated and the Liberals reduced to third-party status.

Layton said the party executive would begin consulting with the NDP caucus to choose an interim leader until he returns to his duties.

But in another surprise move, Layton recommended Nycole Turmel, the NDP's national caucus chair and rookie MP for the Quebec riding of Hull-Aylmer, for the post.

Layton, 61, who represents the Toronto-Danforth riding and has led the New Democrats since 2003, was diagnosed with prostate cancer in late 2009 and went public with it in February 2010. He also underwent hip surgery earlier this year and used a cane during the recent federal election campaign.

Interim leader to be appointed soon

NDP Leader Jack Layton recommended Nycole Turmel, MP for Hull-Aylmer, as his interim replacement. (Nycole Turmel/Flickr)

He said doctors at Toronto's Princess Margaret Hospital found the new cancer last week after he suffered some stiffness and pain in the closing days of the most recent session of the House of Commons.

"My battle against prostate cancer is going very well. My PSA levels remain virtually undetectable," Layton said.

"However, these tests … also indicate that I have a new, non-prostate cancer that will require further treatment. So, on the advice of my doctors, I am going to focus on treatment and recovery."

In a statement, Princess Margaret Hospital said its doctors have been treating Layton for prostate cancer since his diagnosis.

"Recently, new tumours were discovered which appear to be unrelated to the original cancer, and Mr. Layton is now being treated for this cancer," the hospital said.

PM hails Layton's 'tireless determination'

Tributes and messages of support from Layton's adversaries in the House of Commons began pouring in shortly after his announcement.

The prime minister offered his "heartfelt support" for Layton and his family and wished him a "successful recovery so he can return to his post."

"I salute the courage Mr. Layton continues to show in his fight against cancer, a fight that more and more Canadians are winning," Harper said in a statement.

"We are all heartened by Jack's strength and tireless determination, which with Mr. Layton will never be in short supply."

Layton spoke to both Harper and Quebec Premier Jean Charest after the announcement, NDP spokeswoman Kathleen Monk said.

"The call with the prime minister was very interesting. Very personal. They have known each other for a number of years now … so they were talking about their families and vacation," she told Peter Mansbridge, CBC's chief correspondent.

Monk said Layton got the test results last Wednesday and told top level staff the next day.

Interim Liberal Leader Bob Rae said he was stunned by the news and also wished Layton a speedy and full recovery.

"I think he made the right decision," Rae told CBC News. "He is a great fighter. I think Canadians admire tremendously his resilience and determination to deal with the prostate cancer. The way he did that very publicly was very courageous."

In a statement, Green Party Leader Elizabeth May also offered her support for Layton.

"From Toronto city council, to heading up the Federation of Canadian Municipalities to leader of the NDP, we have worked together over many years. I join Canadians across Canada who wish him well and pray for his recovery," said May.

Rookie MP tapped for interim leader

Layton did not take questions from reporters, instead leaving NDP president Brian Topp to field queries over what this means for the party as it prepares for its first full session in the House of Commons as the Official Opposition.

Topp said the party would select an interim leader as soon as possible after consulting with caucus Wednesday and bringing recommendations to the party's federal council Thursday morning.

He also defended Layton's recommendation of Turmel over the party's two higher-profile deputy leaders, Thomas Mulcair and Libby Davies, saying it's better not to force the party to choose between the two MPs.

Topp noted that one of Layton's successes as leader has been to build a great team — which includes Turmel, who previously headed the Public Service Alliance of Canada, the country's main union of federal workers, and who defeated Liberal incumbent Marcel Proulx in the last election.

Topp called Turmel "a very high-profile person in Quebec" and said the rest of the country will soon "get to know her well."

Reached by CBC News after Layton's announcement, Turmel said her party's "strong team" will be ready for when Parliament resumes.

"My biggest challenge I have right now is the support I will give to Mr. Layton and for him to focus on his health," she said.

"We have new MPs, that's true, but I've met all of them. They're great people and I know they will do everything they have to do to make sure that we prepare for the fall session."

Liveblog: Jack Layton's announcement

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