NDP leader Jack Layton kicked off his run for the Prime Minister's Office on Saturday with promises to do more to help retirees, struggling families and to improve front-line health services.

Greeted by a raucous crowd of supporters at the Chateau Laurier Hotel near Parliament Hill -- chanting "Jack!" and "NDP!" -- Layton took aim at the record of Prime Minister Stephen Harper while seeking to distinguish himself from rival party leaders Michael Ignatieff and Gilles Duceppe.

"After five years, Stephen Harper has failed to fix what's wrong in Ottawa. In fact, he's made it worse," said Layton, who was joined by his daughter Sarah and his 20-month-old granddaughter Beatrice.

He said Harper has ignored the health-care system and the problems retired people have making ends meet, and instead presided over a string of scandals.

Layton also took aim at the Liberals, saying that voters who want to get rid of Harper should recognize the NDP is best positioned to defeat Tories in many ridings. He accused Liberal Leader Michael Ignatieff of failing to match his words with action and reached out to voters who previously went with the Bloc Quebecois, remarking that a vote for the Quebec party "can't stop Stephen Harper from becoming prime minister."

The swipes at the other leaders stood in contrast to Layton's overall message of co-operation. Layton has said he would be open to forming a coalition government should the need arise -- an option the Liberals have already ruled out -- and he repeatedly spoke of the need to bring people together

"I'm asking for a mandate to lead the next government," he told the crowd. "If that turns out to be a minority Parliament you can count on me to reach out to all members of Parliament who believe in building a better Canada."

Layton will face questions about his health and possible criticism for triggering the election during the run to the May 2 vote. Party officials insist his health is fine, though he continues to walk with a cane following his recent hip surgery. He is also being treated for prostate cancer.

Conservative Leader Stephen Harper has criticized the opposition for toppling his government and looks to be making it a key point in the Tory campaign playbook, together with the economy. But former NDP strategist Brian Topp on Saturday brushed off the suggestion that voters will hold a grudge over going to the polls for the fourth time in seven years.

"Absolutely not," he told CTV's Lloyd Robertson.

"Canadians like Jack Layton. They trust him. They see him more and more as a guy they'd like to see as an alternative to Stephen Harper," said Topp.

The NDP will be fighting a two-front war throughout the campaign as it looks to take over for the Tories while holding off efforts by the Liberals to siphon away its supporters.

Layton will be holding his first rally in Edmonton later today -- deep in the heart of Conservative country, but a city that elected Alberta's only New Democrat MP in the last election.

"I'm ready to take this fight direct to the Conservative heartland. Starting tonight in Edmonton, where we've shown that only New Democrats are strong enough to defeat the Conservatives," Layton said.

With files from Canadian Press