The federal ethics watchdog is reviewing requests to investigate several Liberal fundraising events, after both the Conservatives and the NDP asked Mary Dawson and federal lobbying commissioner Karen Shepherd to look into "cash-for-access" events.

"The commissioner has confirmed that she has received requests from members of Parliament. She is currently considering those requests and will respond to the members directly in due course," said Marie Danielle Vachon, a spokeswoman for Ethics Commissioner Dawson.

It's unclear if the lobbying commissioner, Karen Shepherd, is conducting a similar review.

In an e-mail to CBC News, Shepherd's office said the "Commissioner takes all allegations seriously. The Lobbying Act requires the Commissioner to conduct all investigations and reviews in private."

The Liberals have faced significant criticism from both opposition parties over $1,500-a-head fundraising events.

In a Dec. 5 letter to both commissioners, interim Conservative leader Rona Ambrose called attention to several stories reported by The Globe and Mail, which describe gatherings involving Prime Minister Justin Trudeau and Bill Blair, the parliamentary secretary to the minister of justice.

"These cash-for-access events appear to provide several examples of violations of the Conflict of Interest Act, the Lobbying Act and the Lobbyist Code of Conduct," Abrose alleges in the note.

The NDP's deputy ethics critic Alexandre Boulerice wrote a similar letter, alleging "such potential violations are serious and that is why I am asking you to examine if there are grounds to initiate an investigation."

Rules followed: Trudeau

Both Ambrose and NDP Leader Tom Mulcair used the opening round of Wednesday's question period to attack Trudeau's participation.

"Does the prime minister understand that this was not only unethical, it's more than likely illegal — or does he just not care anymore?" Ambrose asked.

"There are a lot of questions about these issues. But that's why it makes me happy to reassure Canadians that indeed we have among the strongest political financing rules in the country, which means that Canadians can have confidence in the transparency, openness, rigour, accountability of our system, which this party has always followed and always will follow," the prime minister replied.

"Liberal party fundraisers are not the place to draw in foreign investment," Ambrose said later. "Why has the prime minister so blantantly and so eagerly thrown his ethical guidelines out the window?"

"A frustration around ethics was part of why we got elected in the first place," Trudeau replied.

Mulcair joked it was great to see the prime minister in question period, "really," a jab at Trudeau's recent attendance record.

In Question Period, NDP Leader Tom Mulcair calls into question both the Prime Ministers' lack of attendance in the House of Commons and the Liberal fundraising controversy. 1:15

"I feel kind of lucky because I didn't have to pay $1,500 to get in here," Mulcair said. "Will he now admit that he has used his official position to pour hundreds of thousands of dollars into the coffers of the Liberal Party of Canada?"

Trudeau repeated that his government understands the values that are required to maintain Canadians' trust.