PARIS - The prime minister is playing down concerns that sensitive government information might have been leaked after Maxime Bernier left classified documents at the home of his then-girlfriend, who has past ties to criminal bikers.

And Stephen Harper says he has no reason to believe that anyone planted listening devices in Julie Couillard's apartment, as she has claimed.

"I have absolutely no information that would suggest that is true," Harper said Tuesday in Paris, where he started a three-day European trip.

Harper said Bernier, who resigned Monday as foreign affairs minister, broke rules by leaving the documents. But he added that the papers have now been returned to the government and there's no security concerns.

In Ottawa, government House Leader Peter Van Loan confirmed that the documents were related to a NATO summit held in April in Bucharest, at which Canada sought reinforcements for Canadian troops in Afghanistan.

Van Loan insisted Harper learned only Monday that Bernier had left the documents unsecured and took action immediately.

But opposition MPs demanded the government explain how no one noticed for five weeks that classified documents were missing.

And they slammed the Conservatives for continuing to insist that Bernier's relationship with Couillard is not a security concern.

Liberal Leader Stephane Dion said Harper's refusal to take the matter seriously - until he finally axed Bernier - showed "appalling lack of judgment."

Had the government treated the affair with the seriousness it deserved, Dion said, it would have discovered the documents were missing weeks ago.

Dion called for a public inquiry into the affair.

But Harper suggested that Bernier's resignation has put an end to the matter and Couillard is of no interest to him.

"As we've said, private lives are private lives and the government of Canada does not intend to get into the business of investigating private citizens.

"This has nothing to do with Madame Couillard. This was the unfortunate error, the unfortunate actions of the minister that are at issue here.

"You obviously don't disclose classified materials and you certainly take adequate care to ensure that they are not disclosed and they are not left behind somewhere."

Couillard said that when she found the material, she contacted a lawyer, and it was returned to government officials. She said she never read the documents.

She also said in a broadcast interview that private-sector experts swept her home for listening devices in the last three weeks as a controversy raged over her recent relationship with Bernier. She said they found evidence that bugs were removed recently, including in the box spring of her bed.

Bernier was the centre of controversy this spring over his relationship with Couillard because of her previous relationships with men connected to Quebec biker gangs - as recently as 2005.

Opposition politicians have demanded answers on how much exposure Couillard had to confidential government material.