The federal Liberals have retained human rights lawyer Cynthia Petersen to investigate harassment allegations made against MPs Scott Andrews and Massimo Pacetti.

Petersen is to present a fact-finding report to Liberal Leader Justin Trudeau to assist him in determining whether Andrews and Pacetti can return to the Liberal caucus and run for the party in 2015.

Trudeau kicked Andrews and Pacetti out of caucus last month after he was told of harassment allegations made by two female New Democrat MPs.

The names of the New Democrat MPs haven't been released publicly. One of the MPs has spoken to journalists on condition of anonymity, and anonymity has also been accorded to the second complainant, although their names are widely known among those who work on Parliament Hill.

Lawyer Cynthia Petersen has been retained by the federal Liberal Party to investigate allegations against two MPs. (Sack Goldblatt Mitchell LLP) Trudeau wouldn't say much about the investigation Friday morning when he spoke to reporters in St. John's.

"We have established a process for Ms. Petersen to look into all the facts that have been made available to us in this case," Trudeau said.

"It's a serious process for a serious set of allegations."

Both Andrews and Pacetti have denied the allegations. None of the allegations have been proven.

No timeline for report

Trudeau said hiring Peterson does not preclude any process through the House of Commons Speaker's office with an additional neutral third party.

"My hope certainly is that the Speaker's independent process is taken up ... but as we know the Speaker's recommendation process will not be determining someone's eventual candidacy for the Liberal Party or not and that's why we needed to set up a process as well," he said.

The New Democrat MPs won't make an official complaint, so the Speaker hasn't been able to proceed.

If Trudeau decides not to allow the MPs to run in the 2015 federal election, which is scheduled for October, then the party would have to find new candidates, a process that can take weeks on top of the pre-election campaigning.

Trudeau would not say whether he'll release Petersen's report to the public.

"I'm not going to speculate one way or the other at this point," Trudeau said on Friday.

There's no deadline attached to the report, but Petersen is expected to try to set up meetings with the four MPs involved as early as over the Christmas holiday break.

Report may be based on meeting notes

The Liberals retained Petersen to "conduct an independent, fair and confidential investigation," said Kate Purchase, a spokeswoman for Trudeau, in an email to CBC News.

It's not clear whether the New Democrat MPs will be willing to sit down with Petersen. The NDP is upset that Trudeau kicked Andrews and Pacetti out of the party, drawing media attention to a situation the women wanted kept private.

New Democrat MP Philip Toone said he hasn't spoken to his colleagues about whether they'll sit down with Petersen.

"I think they're clearly considering their options right now," he told CBC News.

"It's important that we give them the opportunity to reflect, to go through the details, decide if this is the correct process for them."

If the MPs don't co-operate, the report will be based on notes taken by Liberals in initial meetings with the New Democrats. Petersen is to look at those allegations "and any related allegations that may come to light during the course of the investigation," Purchase said.

The Liberals say the NDP were informed Friday morning that Petersen had been retained.

Toone sounded more conciliatory than the New Democrats have been since Trudeau first announced Andrews and Pacetti were out of the Liberal Party.

"The Liberals have decided that for them this new process is going to be good for them. That's fine and I'm glad they have come up with a process that works for them," he said.

Petersen is a partner at Sack, Goldblatt and Mitchell and has been discrimination and harassment counsel for the Law Society of Upper Canada since 2002. The party says she doesn't hold a Liberal membership.