OTTAWA–New Democratic Party Leader Jack Layton vows he'll fight prostate cancer, the disease that his late father, Robert, also battled 17 years ago.

"Like my dad, I am a fighter and I am going to beat this," Layton said Friday, emphasizing that he will be staying on both as the MP for Toronto-Danforth and party leader, a position he has held for seven years.

"This year, more than 25,000 Canadian men are going to be diagnosed with treatable prostate cancer and I recently learned that I'm one of them," Layton told a news conference in Toronto.

"It's the same kind of prostate cancer that my dad was diagnosed with 17 years ago. I intend to bring to this battle the same sense of determination and optimism that he did."

Robert Layton, a Progressive Conservative cabinet minister in Brian Mulroney's government, died in May 2002 at age 76 from complications of Parkinson's disease.

At Layton's side as he spoke was his wife, Olivia Chow, the NDP MP for Trinity Spadina, who successfully waged a battle with cancer of the thyroid.

"She won her battle, and I'm going to win mine as well," he said of Chow, who has been cancer-free since 2005.

Layton said his treatment for the disease had already started.

"I am feeling good," he said.

The 59-year-old Layton, a high school jock who played football and was a champion swimmer, stands out on Parliament Hill for his devotion to fitness.

Even during gruelling election campaigns, reporters were impressed that he always found the time to work out.

Indeed, for the last several weeks, Layton has been nursing a sore back, which he attributed to lifting too much weight at the gym.

When Layton was a city councillor, starting in the 1980s, it was a familiar site to see him riding his bike on the streets of Toronto. Indeed, he hadn't owned a car in decades.

One of his proudest accomplishments was helping to bring in Toronto's pioneering anti-smoking bylaw in the 1980s during his term as chairman of the city's health board.

Liberal Leader Michael Ignatieff said Layton "has fought many battles in his life, but none will be as demanding as the fight he now faces."

"We all know how combative Jack is and we know that he will face this challenge with his usual determination. I wish him strength and courage on the road to recovery, and I know all Canadians stand behind him in this fight," Ignatieff said.

Prime Minister Stephen Harper said his concern for Layton trumps any political differences they have.

"Our thoughts and prayers will be with him, and I look forward to doing political battle with him for many years to come," he said.

Layton, who plans to hold a press conference in Ottawa Monday, joked that the treatments could mean he will be watching more of the Vancouver Olympics than he had expected.

"I can be inspired by our athletes as they exercise their determination," he said.

Layton was diagnosed late in 2009 during a routine checkup, said his press secretary Karl Belanger.

"He will be treated here in Toronto," said Belanger, standing inside a packed Estonian Hall on Broadview Ave. in east-end Toronto.

Belanger would not say how long and what type of treatment that will be.

Dr. Robert Siemens, a professor at Queen's University medical school, told the Star prostate cancer is the most commonly diagnosed cancer in men and one of the most treatable.

"In most men, the natural history is quite long, so therefore when we catch it early we feel that it's very treatable," Siemens said.

Layton has brought a higher profile and increased public funding to the party since he took over as leader in 2003. He marked his seventh anniversary in the job last week.

In a string of elections under his leadership, the party has boosted its seat count in the House of Commons – to 37, up from 14 – and its share of votes.

"There is a lot more to do," Layton told reporters Friday. "There is still work ahead of us to build that caring and green Canada that we believe in and know is possible and I can't wait to roll up my sleeves Monday morning and get started."

Any suggestion Layton won't be able to keep up the pace or that the party will founder was quickly dispelled by one of the NDP's two deputy leaders.

"We and the rest of the team will be there to step in for Jack if need be to help out a bit more. He always was there for us and we are going to be there for him," said MP Thomas Mulcair (Outremont).

As recently as Thursday evening, Layton was in fine form at a party marking the end of the unsuccessful provincial by-election campaign for Toronto Centre NDP candidate Cathy Crowe.

He fired up a crowd of more than 300 New Democrat partisans with a passionate address, did live television hits for CP24, and, with Chow, energetically worked the party late into the evening.

The birth of his first grandchild last summer put Layton on Cloud Nine and he proudly announced he had spent part of his summer holiday happily pushing a baby carriage through downtown Toronto.

-With files from Bruce Campion-Smith and Robert Benzie