Washington  - Canada's Foreign Minister Maxime Bernier has resigned Monday after he admitted to leaving sensitive government documents out in the open at a private residence, reported Canada television.

"This is a serious error," Prime Minister Stephen Harper said. "The minister has recognized this error himself and offered to resign."

The sensitive documents, which included classified information about NATO, were left behind at his ex-girlfriend's house in mid-April, according to CTV news.

Bernier, 45, has come under fire in recent weeks after it was reported that his ex-girlfriend, Julie Coulliard, 38, had previous relationships with men linked to organized crime.

Couillard appeared on a French-language Canadian television show Monday night to say that her former boyfriend was careless with classified documents.

"Maxime came to see me and he left a document behind," said Couillard in the 24-minute-long interview. "The document was given back." She added it was left by accident.

Couillard's past links to Quebec bikers - she was married to a member of the Rockers biker gang, and dated another Hells Angels biker - have come under scrutiny.

She started dating Bernier before his swearing-in in August 2007 and their relationship ended a few months ago.

Trade Minister David Emerson will take over Bernier's post on an interim basis. (dpa)