CALGARY -- Prime Minister Stephen Harper is sticking to his story in the Senate expense scandal, maintaining his former chief of staff acted alone in paying Mike Duffy's invalid expense claims.

Harper repeated on Saturday that it was Nigel Wright's decision to give Duffy $90,000 out of his own pocket to reimburse the Senate and he must take the responsibility.

"It was a decision of Mr. Wright and he will be held accountable for that," Harper told a news conference that he called to comment on a train derailment and fire in Lac- Medantac, Que., earlier that day.

Court documents released Friday contradict Harper's version of the events involving Wright's payment to Duffy.

RCMP said in one of the documents that Wright recalled telling three other senior employees in the Prime Minister's Office about the payment. The claim is at odds with Harper's assertion in the House of Commons last month that his ex-chief of staff didn't tell him or anyone else in his office about handing over the money.

However, Harper said Saturday that he doesn't see any contradiction.

"I think if you read the affidavit it makes very clear that the decision to pay money to Mr. Duffy out of Mr Wright's personal funds was made solely by Mr. Wright and was his responsibility," Harper told the news conference.

"Obviously, had I known about this earlier I would never have allowed this to take place. When I answered questions about this in the House of Commons I answered questions to the best of my knowledge," said Harper, who reiterated he only learned of the matter when it became public in mid-May.

Wright's lawyers back up Harper's contention in the court documents.

However an opposition MP said he doubts Canadians are buying that Harper knew nothing about the payment.

"It's really depressing to see the prime minister of Canada acting like the piano player in the bordello saying he didn't know what was going on upstairs," said New Democrat Charlie Angus.

"I think given what's coming out in the affidavits what's coming out in the police investigation, Mr Harper's excuses are wearing a little thin and he needs to do better."

Wright had not been interviewed by Mounties at the time the document was filed in court by lead investigator Cpl. Greg Horton, on June 24. But the document recounts a June 19 meeting with Wright's lawyers, Patrick McCann and Peter Mantas.

The lawyers told the RCMP that Wright recalls telling his assistant, David van Hemmen, Harper's legal adviser, Benjamin Perrin, and Chris Woodcock, director of issues management in the Prime Minister's Office, about his intention to give Duffy the money to reimburse the Senate for dubious housing expenses.

Perrin, who has since left the PMO, has denied he was consulted or participated in any arrangement between Duffy and Wright.

On Saturday, Harper did not address the claim in the document that Wright told senior members in the PMO about his plans to make a payment.

Wright resigned as Harper's chief of staff in May, five days after news of his "gift" to Duffy leaked out.

Opposition parties said Friday that the court document shows Harper misled Parliament.

According to Horton, Wright also told Sen. Irving Gerstein, who controls the Conservative party's purse strings, about his intention to give Duffy the money to reimburse the Senate.

Wright's lawyers told the RCMP the party was initially prepared to repay the money for Duffy, until it discovered the price tag was three times steeper than originally thought.

Wright then offered to cover the cost for Duffy.

Horton noted in the documents that the RCMP has not yet interviewed Duffy or Wright.

The scandal revolves primarily around Duffy's claim that his primary residence is a cottage in Prince Edward Island, not his longtime home in Ottawa. It has expanded to involve ineligible Senate travel expenses Duffy claimed while on vacation or campaigning in the 2011 election for Conservative candidates, who also paid his expenses.