Newly-elected NDP leader Thomas Mulcair says his number one goal is to draw new, younger members to the official opposition party.

"That's part of our challenge now," Mulcair told CTV's Question Period. "Reach out beyond our traditional base, talk to people who share goals and values with the NDP but haven't voted for us, but have stopped voting.

"That's our number one target audience for the next election." Mulcair won the leadership Saturday night with 33,881 votes from party members, taking 57.1 per cent of support after the fourth round of voting.

The Montreal MP said it's also crucial that the party hold onto the gains made last election in Quebec. Without that base, the NDP's stated goal of forming the next government won't ever materialize, he said.

The Montreal MP brushed off the criticism leveled by the Conservatives mere minutes after he was crowned leader Saturday night. In a news release, the Tories described Mulcair as opportunistic and divisive.

Mulcair said the comments say more about the Conservative Party than reflect badly on him.

"Some of those attacks are like Grade 9," Mulcair said. "It's so puerile. It's so infantile. But I think that that average Canadian voter is growing tired of it. "

Mulcair said the sharp public jabs could backfire on the Tories.

"The more the right wing attacks the political class generally . . .the more people turn off from voting," he said. "Forty per cent of Canadians didn't bother to vote in the last elections, 65 per cent of young people age 18 to 25 didn't bother to vote."

Yet, Mulcair, a onetime professor, lawyer and Quebec MLA, said he's no political shrinking violet, noting he learned the "rough and tumble of politics" in the Quebec legislature facing off against the Parti Quebecois.

He said the Tories are an ideologically driven, tough party that sometimes believes it's above the rules.

"They believe that they're serving a higher cause," Mulcair said. "That sometimes also leads you to believe that the normal rules don't apply. For example, the robocalls, you know, that's depriving people of their most basic right in a democracy-- their right to vote."

Mulcair's path to victory wasn't entirely smooth. He faced criticism from within his own party when former leader Ed Broadbent questioned his leftist credentials. Broadbent, who backed runner-up Brian Topp, said he worried Mulcair would steer the party to the centre.

However, Mulcair suggested that rift has healed, noting that Broadbent publicly congratulated him. He also took pains not to criticize opponents during the leadership race.

Caucus meeting

On Sunday, Mulcair met with his 101 caucus colleagues at a Toronto hotel, as well as the party's federal council, moving to heal the wounds from the seven-month leadership contest.

"Together, united, we're going to face our only adversary, Stephen Harper's Conservatives, starting tomorrow!" he told pumped New Democrat MPs as they chanted his first name.

Mulcair, clad casually in blue jeans and an open-collar shirt, seemed unfazed by the Conservative attacks from the night before.

If anything he praised the Tories' discipline and suggested the NDP would do well to emulate the ruling party.

"Right now we're facing a government that's very tough, very well structured, and we've got to do the same thing," Mulcair told reporters.

"We've got to structure an official Opposition that will bring the fight to them like they've never seen before."

Mulcair also put to rest suggestions that he might punish colleagues who supported rival candidates or sideline members of Layton's inner circle -- most of whom had backed Topp.

He said Vancouver MP Libby Davies, a Topp supporter, will remain a deputy leader and that Anne McGrath, one of Layton's closest confidants, will stay on as chief of staff through a transition period.

And he said he'll be keeping "98 per cent" of the party's existing management team.

He said he won't touch the lineup of the NDP shadow cabinet for the next couple of weeks, unwilling to disrupt the parliamentary team as it prepares to respond to Thursday's crucial, cost-slashing federal budget.

Minister warns of ‘vicious' streak

Meanwhile, Conservative cabinet minister James Moore, racheted up the criticism Sunday, saying Mulcair has a renowned "vicious" streak that has turned off senior New Democrats such as Alexa McDonough, Libby Davies and Roy Romanow.

"I think that's a lot different than Stephen Harper," Moore told CTV's Question Period. "There's a difference between a strong, firm leader and someone who is really vicious and personal."

Moore warned that the NDP under Mulcair would lead Canada to "the hard left, bigger taxes, bigger government, more central control over people's lives."

Mulcair's election caps months of soul-searching by the NDP, which made historic gains in the 2011 federal election under the leadership of the late Jack Layton, who vaunted the party to official opposition status for the first time.

Layton's death from cancer last August threatened to undermine those gains. But Mulcair said he has every intention of leading the NDP to form the next government.

Meanwhile, Mulcair's election Saturday underscores the Liberal party's leaderless status. Bob Rae has been serving as interim leader since Michael Ignatieff resigned after his defeat in the May 2011 election.

Rae said he doesn't feel pressure to hold a leadership convention. Right now, the Liberals are concentrating on rebuilding a national party and performing effectively in the House of Commons.

"We've got an effective three-party system," he said.

Mulcair, 57, becomes Canada's 44th Opposition leader, and he promised to take on the role without using the politics of division.

"Leadership comes in many forms. Our current government appeals to peoples' fears and rules by seeking division," Mulcair said in his victory speech Saturday. He did not directly mention Prime Minister Stephen Harper's Conservatives.

"We will unite progressives, unite our country, and together we will work towards a more just and better world."

Six other candidates arrived in Toronto vying for the party's top job, including Topp, the former party president and dark-horse candidate Nathan Cullen, who finished second and third, respectively.

Topp, who was the only candidate without a seat in Parliament, had cast himself as the true heir to Layton, and often spoke of his final moments with the late leader on his deathbed last August.

Topp had been a key member of Layton's inner circle and has been credited with engineering the Quebec-based surge that led to the NDP's electoral breakthrough last May, when the party pushed their seat count to more than 100 for the first time.

Topp's traditionalism versus Mulcair's modernizing push became the central debate in the party's seven-month long leadership campaign.

But ultimately, Mulcair's vision prevailed.

"In order to win the next election and have our first NDP federal government, our party much reach beyond its traditional base and unite all progressive forces under the NDP banner," he said, with Topp standing nearby.

"We won't do it by sacrificing the unity of our country."