OTTAWA -- The opposition says it is startled by the insistence by the Prime Minister's Office that there's little chance Stephen Harper will have to testify at Sen. Mike Duffy's criminal trial.

"It's remarkable that the prime minister's office has decided that they would comment on this matter before the courts when they normally do not comment on matters before the courts," Liberal MP Geoff Regan told an Ottawa news conference.

"In my view, it's a matter for the courts to determine whether or not Mr. Harper should testify."

Jason MacDonald, a spokesman for Harper, said on Tuesday it was "difficult to imagine" the prime minister testifying because the RCMP have made it clear they don't believe the prime minister has any knowledge of Duffy's alleged wrongdoing.

In an email, he added there would be no reason for the prime minister to be involved should Duffy's defence team attempt to call him to the witness stand.

The NDP's Peter Julian said he suspects the PMO, via MacDonald, is trying to send a message to the courts about Harper's reluctance to testify.

"I think he's flagging it in a subtle way," Julian said in an interview.

"His office seems to be indicating that he's not going to be forthcoming and I think that's a big mistake. Canadians have a strong expectation that Mr. Harper is going to start answering questions."

The RCMP announced last week it was charging Duffy with 31 criminal counts related to his expense claims, accusing him of misspending more than $200,000.

The charges stem from the disgraced senator's housing and travel expenses, and a $90,000 payment from Nigel Wright, Harper's former chief of staff.

Earlier this week, a new court filing provided fresh details of the RCMP's charges against Duffy, alleging he billed taxpayers for a personal trainer, a makeup artist and for personal travel to funerals.

Neither Duffy nor his lawyer have responded to a request for a comment on MacDonald's comments. The 68-year-old senator is scheduled to appear in court on Sept. 16, and has denied any criminal wrongdoing.

It's been a trying few days for Duffy. The lawyer for a 32-year-old Peruvian woman who claims she is Duffy's "love child" says the former CTV newsman reached out to her this week.

Jorge Alejandro Razuri said on his Facebook page that Duffy has been in touch with Karen Duffy. It wasn't immediately clear if that meant her court action against him to establish paternity has been dropped.

"Out of respect for the parties we will not be making any further comments or statements at this moment," Razuri wrote.

The Liberals are calling on the federal ethics watchdog to re-open her investigation into the Senate expense scandal, a scenario Mary Dawson's office suggested wasn't on the immediate horizon.

Regan wrote to the ethics commissioner, saying it is time for a renewed probe now that Sen. Mike Duffy has been formally charged.

The Liberal MP says that since the RCMP has concluded its investigation, there's no reason to delay an ethics probe. Dawson had launched an investigation last year, but suspended it when the Mounties announced their criminal investigation.

"It would seem that there is no longer any impediment to the resumption of your original investigation," Regan wrote in a letter to the commissioner.

"I would ask that you please detail any plans to resume your ethics investigation, including for those public office holders who are not under criminal indictment."

But a spokeswoman for Dawson said the commissioner wasn't yet prepared to re-open her investigation.

"Commissioner Dawson's examination under the Conflict of Interest Act of the conduct of Mr. Nigel Wright remains suspended at this time," Jocelyne Brisebois said in an email. "She expects to resume the examination as soon as it is possible to do so."

In a court filing in November, the RCMP identified a number of people who may have been linked to the scandal, including five senators, Conservative party officials and some employees in the prime minister's office.

"The RCMP documents allege that many of these public office holders clearly had knowledge of the $90,172.24 cheque which led to Mike Duffy being charged under the Criminal Code's bribery of judicial officers section," Regan said in his letter.

In April, the RCMP concluded there wasn't enough evidence to charge Wright, who resigned after it was revealed that he provided Duffy with the money to help him cover his expenses.