The Opposition demanded Monday that Prime Minister Stephen Harper answer questions in the House of Commons about the ongoing Senate expense scandal, including the $90,000 payment from his chief of staff to Sen. Mike Duffy to pay back the senator’s ineligible housing expenses.

Harper, back from a trade trip to Latin America, did not appear for question period, leaving Heritage Minister James Moore to defend the government.

NDP Leader Thomas Mulcair said Harper attacked then-prime minister Paul Martin for pleading ignorance about the sponsorship scandal, and asked why Harper appeared to be doing the same.

“There we go with the Conservative playbook. Plan A is to hide out in South America. Plan B is to blame the Opposition. Why do they not try Plan C, which is to start telling Canadians the truth?” Mulcair asked.

“For the Conservatives it is business as usual. Does the prime minister think it is business as usual for a Senator to defraud taxpayers? Is it business as usual to give a $90,000 payout? Dodging questions about political payouts was shameful when Paul Martin did it. Why does the prime minister think it is just business as usual today?”

Moore responded by calling on the NDP to support the Conservatives’ efforts at Senate reform.

“We have legislation for Senate elections and legislation for term limits. Even the idea of abolishing the Senate requires a mandate from the Supreme Court to understand the mandate capacity of the House of Commons, which is what we have done. However, the NDP are even against that,” Moore said.

The prime minister has not faced the Opposition in the House since the scandal broke two weeks ago.

However, while in Peru last week, Harper told reporters that he only learned of the $90,000 cheque from Nigel Wright to Duffy when it was reported by CTV’s Ottawa Bureau Chief Robert Fife. He apologized for the conduct of some parliamentarians and office staffers, and said he never would have approved such a deal had he known about it.

Harper’s staff said he would be attending question period on Tuesday.

On Monday, Liberal Leader Justin Trudeau said his party was moving a motion calling on the House Ethics Committee to “study the scandal facing the PMO and to offer the prime minister and Nigel Wright an opportunity to bring transparency to this issue.”

Moore replied that the committee is already probing the issue, “as is the Ethics Commissioner, as is the Senate office of ethics, and that is where these matters will be addressed.”

The Conservatives killed the Liberals’ motion.

Moore also criticized Trudeau’s recent comments on Senate reform, in which he told a Quebec newspaper of his opposition to abolishing the upper house. He noted that Quebec has more seats than Alberta and British Columbia.

“We have 24 senators from Quebec and there are just six from Alberta and six from British Columbia,” Trudeau said according to the newspaper report. “That’s to our advantage.”

Trudeau told reporters that he did not regret making the comments, saying he was merely stating a fact, not opinion, about the “numerical reality of the Senate and the challenges around reforming it.”

Trudeau added: “I am a Quebecer and from time to time when I am speaking with Quebecers I might use the word ‘we.’ However, in my choices of policy, in my approach to this country, I have always spoken for and to and with all Canadians and I will continue to.”

Trudeau is opposed to the NDP’s notion of abolishing the Red Chamber, and instead is calling for an elected Senate.

With a report from CTV’s Daniele Hamamdjian