Prime Minister Stephen Harper says his office is not under investigation by the RCMP, a day after CBC News reported the Mounties are looking for a chain of emails and documents that support Mike Duffy's allegations the Senate expenses scandal reaches into the Prime Minister's Office.

CBC News reported on Monday the RCMP believe "the existence of such documentation may potentially be evidence of criminal wrongdoing by others."​

The prime minister rejected NDP Leader Tom Mulcair's assertion in the Commons on Tuesday that "the prime minister's own office is under criminal investigation by the RCMP."

"Of course that statement is not true. As we know, certain individuals and some senators are under investigation," Harper said.

The Nov. 1 letter by Supt. Biage Carrese from the RCMP National Division was obtained by CBC News on Monday and subsequently released publicly by Duffy on Tuesday.

When Mulcair asked the prime minister to confirm whether the RCMP had requested documents originating in his office, Harper said the Mounties were seeking documents from Duffy, not his office.

"I think what the leader of the NDP is referring to is a letter the RCMP has written, I gather, to the lawyer for Mr. Duffy urging him to co-operate with the RCMP investigation. Of course, we would all urge that," Harper said. 

"This office will give the RCMP any and all assistance it requires."

After question period, CBC News contacted the Prime Minister's Office for further clarification on whether police have asked it for documents and whether the PMO provided them.

In an email to CBC News, Jason MacDonald, the director of communications for Harper, said "Yes. We have actively assisted them."

Who in the PMO knew?

The prime minister maintained he had no role in the decision by Nigel Wright, his former chief of staff, to give Duffy $90,000 out of his own pocket to repay his ineligible expenses, "or about the story to deceive Canadians about that."​

Of particular interest to the Mounties, according to the letter, are Duffy's allegations in the Senate last week that his initial story about repaying his disputed expenses by taking out an RBC loan was fabricated by senior advisers to the prime minister.

"Emails from the PMO specifically relating to a script for Senator Duffy to follow in advance of obtaining funds from a RBC loan to repay the Receiver General" may be material to the RCMP's investigation, Carrese said in the letter.

On Tuesday, Duffy would not say whether he or his lawyer had turned over any emails or documents to the RCMP since receiving the Nov. 1 letter.

"It would not be appropriate for me to comment while the RCMP are investigating," Duffy told CBC News in an email.

Liberal Leader Justin Trudeau asked Harper whether Senator Irving Gerstein — who conceded that he and Wright did discuss paying back Duffy's inappropriate expenses — had told Harper about that discussion.

The prime minister said "no," his chief fundraiser had not made him aware of that discussion.

But if Gerstein knew about the Wright-Duffy scheme and kept it a secret from Harper, "why is he still the prime minister's chief fundraiser?" Trudeau asked.

Harper did not answer the question directly, but Mulcair picked up where Trudeau left off, asking the prime minister why he would not take responsibility for Gerstein's role in the Wright-Duffy affair.

Harper said he had been told that Duffy had repaid his inappropriate expenses and when he found out that was not the truth, the prime minister told the Commons, "I took my responsibilities and made the appropriate changes in my office."