Conservative leader Andrew Scheer says he has instructed his party to launch an independent investigation into questions surrounding Rick Dykstra's federal candidacy in 2015.

Dykstra, a former Conservative MP, resigned as president of the Ontario Progressive Conservative party on Sunday. Hours later, Maclean's magazine published a report saying Dykstra had been accused of sexual assault in 2014.

According to Maclean's, Conservative party officials allowed Dykstra to stand as a candidate in 2015 despite the allegation.

CBC News has not spoken to the person who made the allegation against Dykstra.

"It is difficult to ascertain the facts when sources are speaking anonymously to the media. So to gather these facts, I have instructed the Conservative Party of Canada to retain the services of an outside, independent third party, who can investigate this situation fully," Scheer said on Wednesday.

Conservative Leader Andrew Scheer says he has called for an independent investigation that the party knew about allegations of sexual assault by one of it's MPs. 3:35

The report will be made public, a party spokesperson confirmed.

In his initial response to the Maclean's report, Scheer said he could not speak to "decisions made by past campaign teams" and he did not speak to reporters after meeting with the Conservative caucus on Wednesday morning.

But some Conservative MPs had begun calling for an investigation.

"I don't know why the party didn't do anything at that time and they have to answer these questions," Maxime Bernier told reporters on his way to the caucus meeting.

"The party must respond. They're the ones who had these facts at the time and I think that they have to tell us what happened."

Brad Trost later tweeted that Bernier was "110% right. There absolutely needs to be an investigation launched."

"I don't want this to be a backwards-looking witch hunt," Erin O'Toole told reporters, "but I want us to make sure we learn from it and never allow such a situation to arise again."

Scheer said the Conservatives would also be "strengthening the code of conduct for all party staff, and ensuring candidates are subject to it as well. The additional measures will include mandatory training."

During debate in the House of Commons on Monday, Conservative MP Michelle Rempel criticized the reported response of some in her party to the allegations against Dykstra.

"Is it possible for a drunk staffer to give consent for sex to a senior male within their workplace organization who aggressively propositions that staffer? Within any standard workplace code of conduct, the answer to that should be unequivocally no," she said.

Scheer was also asked whether he felt he had ever acted inappropriately in the past.

"No," he said. "A good friend of mine when I first got elected said nothing good happens in Ottawa after 8:00 and I've tried to live by that rule."