A young and untested NDP caucus dove into the first day of the new parliamentary session on Monday, facing lingering questions about who will lead their party against a veteran Conservative government.

In what could be cast as a David and Goliath-like struggle, Interim NDP Leader Nycole Turmel led off question period against a prime minister armed with a battle-hardened caucus and a long-coveted majority mandate.

Adding to the first week jitters on Monday were indications that stalwart NDP Montreal MP Thomas Mulcair, who has been considered as a replacement for the late Jack Layton, indicated that he may not seek the party's top job.

Pointing to questions about membership numbers and provincial party support in Quebec, Mulcair said that he would face an uphill battle if he decided to go for the leadership position.

"I'm getting a lot of support and encouragement from across Canada but that's the simple mathematical model that I have to deal with," he said.

"So, when I say that I haven't reached any decision yet, I'm not playing coy. It's a simple statement of fact."

Though Mulcair suggested the party provide money for a Quebec membership drive, his statements did little to calm simmering concern about his party's unity and their ability to be an effective Official Opposition without Layton at the helm.

During her first question, Turmel asked Harper in French about his government's plan for creating jobs as the global economy appears to be heading back into recession.

Harper responded by congratulating Turmel on her first question as leader, and said that the government will be spurring the economy by investing in research, development and other areas.

But when Turmel followed up with a statement that the economy needs 420,000 new jobs to get back to where it was before the recession started, Harper used his response as a platform the trumpet his party's economic track record.

"There are more people working in Canada today than before the recession, the only advanced country where that is the case, and that is because the government remains focused on jobs," he said.

Later, Turmel told CTV's Power Play that the day's proceedings forced her to switch gears, since the morning was marked by a tribute to Layton while the afternoon session featured traditional political sparring.

"We were ready for this session," she said, noting that the caucus worked hard last week in preparation.

When facing the reality that she is the leader, despite her rookie status, she referred to Layton's judgment and said that it continues to provide her with the confidence to get the job done.

"I still think about the fact that Mr. Layton trusted me, and put me in this position."

Meanwhile, government House Leader Peter Van Loan said the key items in the fall session will be a budget implementation bill and an omnibus crime bill.

"On May 2nd Canadians gave our government a strong mandate to implement our platform. They asked us to go to work and deliver on our commitments," Van Loan said.

The budget implementation bill will include a hiring credit to help small businesses create new jobs, and a tax credit for families that enroll their children in art, music or dance lessons.

The government will also reintroduce free-trade agreements that were previously tabled but never voted on in the House of Commons.

"We look forward to working with the opposition to pass these important bills that will create jobs," Van Loan said.

The crime bill will include a number of longstanding Conservative commitments on everything from young offenders, to terrorism and preventing human smugglers from abusing the immigration system. Van Loan pledged the bill will be voted into law within 100 sitting days.

He said the elimination of the long-gun registry will be a priority for the fall, but will not be included in the crime bill.

"We set out to Canadians what we want to do in the last election, they heard our commitment and they gave us a majority mandate to deliver on that commitment to combat crime," he said.

The Conservatives will also introduce measures to redistribute federal seats, an initiative designed to "move closer to the principle that every vote should be of equal value," Van Loan said.

They will also take steps to eliminate the Canadian Wheat Board's marketing monopoly in Western Canada.

Layton tribute

The parliamentary summer break was marked by the death of Layton, who was remembered by MPs who offered tribute to the late NDP leader on Monday.

Layton died from a new, undisclosed form of cancer on Aug. 22, 2011.

Parliamentarians shared fond memories of the scrappy leader who spent years at the helm of the third-place party, finally bringing it to Official Opposition status just before his death.

"Mr. Speaker I rise to address the House today beside an empty chair. In it sat a great Canadian, a great leader and a great parliamentarian. Mr. Speaker, in this chair sat a friend," Turmel said, followed by thunderous applause.

Harper also paid tribute to Layton's character, despite their often opposing political views.

"Notwithstanding the personal challenges in front of Jack and regardless of the personal combat going on between us he was still, as always, full of optimism and goodwill," Harper said in Commons.

Layton's widow Olivia Chow said the messages of hope and inspiration that she has received from Canadians have been "a source of great strength for me and for our family."

Right up until his death, and even afterwards in a letter written to Canadians that was released after he died, Layton called for less partisanship and more co-operation between the parties.

The Conservatives will be up against two opposition parties led by interim leaders. Bob Rae is at the head of the Liberals, while Turmel is in charge of the NDP until it elects a new leader sometime next year.