The NDP made Prime Minister Stephen Harper their first target as Parliament resumed today, questioning what he knew about a deal between Senator Mike Duffy and his former chief of staff.

NDP House Leader Nathan Cullen and whip Nycole Turmel also set out a proposal to stop government MPs from pushing committees in-camera.

In question period, New Democrat Leader Tom Mulcair set his sights on Harper, who left Thursday morning for Brussels to sign a tentative trade deal with the European Union.

Mulcair listed a number of people close to Harper who are now under scrutiny over corruption or other allegations of wrongdoing, including senators, Harper's former chief of staff, Nigel Wright, and his former parliamentary secretary, MP Dean Del Mastro, who faces charges over his election spending.

"These are chosen members of the prime minister's own inner circle implicated in scandal," Mulcair said.

"The prime minister needs to take responsibility for the climate of corruption that he created. Instead the prime minister flies off to Brussels … When will the prime minister stand up in this House and tell the truth to Canadians?"

Pierre Poilievre, minister of state for democratic reform, accused the NDP of being anti-trade.

"Once again the leader of the Opposition attacks our prime minister for travelling abroad to conclude the biggest trade agreement since NAFTA," he said.

"The NDP would simply like to build a big brick wall around Canada. A brick wall that would keep out 80,000 jobs, that would keep away 500 million customers, that would keep away $1,000 in increased income for the average family."

Limiting secret committee meetings

Earlier Thursday, Cullen and Turmel announced New Democrat MPs would push for committees to be more open.

Committees can go behind closed doors for planning purposes or when preparing a report, but Conservative MPs have been pushing them in-camera more and more than previous governments. They often use the tactic to kill opposition motions in secret. Conservative MPs form the majority on all parliamentary committees.

MPs are also forbidden from discussing what goes on behind closed doors afterward.

"The minute Conservatives don't like a discussion that's taking place in any of our committees, they go in-camera and shut the door on Canadians," Cullen said.

"The abuse of this in-camera tool is undermining the work of all members of Parliament and increasing the skepticism of the Canadian public."

New Democrat MPs will present motions in all committees next week, Cullen and Turmel said, laying out specific instances in which they can go in-camera:

To discuss wages, salaries and other employee benefits, contracts or other labour or personal matters.

For briefings concerning national security.

To discuss draft reports.

The motion also mandates that minutes be taken, including how each member votes when votes are taken.

NDP on offensive

"As parliamentarians, we must be accountable to those who elected us," Cullen said, adding that towns and school boards use the same rules the NDP want to see in Parliament.

"In a healthy democracy, shutting the doors on debate should be limited to only the most exceptional circumstances."

The Official Opposition hit the Hill on the offensive this morning.

NDP ethics critic Charlie Angus raised a question of privilege, which the party announced Wednesday. Angus is asking House Speaker Andrew Scheer to find Prime Minister Stephen Harper misled the House, when he said nobody in the Prime Minister's Office knew about a deal between Wright and Senator Mike Duffy.

Wright paid back Duffy's wrongly claimed Senate expenses. An ongoing RCMP investigation into the payment, and into Duffy's expense claims, alleges Wright told them three other PMO staffers, plus Senator Irving Gerstein, about the agreement.

The Senate committee in charge of financial and administrative matters, the board of internal economy, met Thursday at 9 a.m. ET.

The Senate as a whole will resume at 2 p.m. with a new government leader, Claude Carignan, and deputy leader, Yonah Martin. But unlike his predcessor, Carignan will not sit in cabinet.

Harper has removed the Senate leader from cabinet for the first time in 50 years.

One of the Senate's first acts was to move to suspend without pay Duffy and Pamela Wallin, who is also under investigation by the RCMP.