OTTAWA—The Prime Minister’s Office has warned senior political staff across government not to interfere in the handling of access to information requests.

The warning comes as opposition MPs are calling for an independent investigation into “all instances of Conservative interference” to foil the release of information.

Guy Giorno, Stephen Harper’s chief of staff, penned a memo on Tuesday to chiefs of staff in federal departments reminding them to “respect” the access to information process, a senior official said.

And they were pointedly warned that it’s an offence to deliberately obstruct access requests.

Giorno fired off the memo after the revelation that an aide to federal cabinet minister Christian Paradis blocked the release of a sensitive report requested under freedom-of-information even though it had been approved by public servants.

“Well unrelease it,” Sebastien Togneri, Paradis’ parliamentary affairs director, said in an e-mail obtained by Canadian Press to a senior official in the department’s Access to Information section.

The document was an annual report on Public Works’ huge real-estate portfolio, containing information on high vacancy rates and weak returns on investment. Such reports had never been made public before.

On Tuesday, Harper’s office sought to distance itself from suggestions of a cover-up, saying political staff should have no involvement in access requests.

“Obviously, around Access to Information, due diligence is and should be done by public servants and not political staff,” Harper spokesperson Dimitri Soudas said.

According to a senior government official, Giorno’s memo warned that the access to information process “should be followed and respected by all.

“It applies to everybody across government, including political staff,” the official said.

And he said that subject to access to information rules, residents have a right “to be given access to any record under the control of a government institution.”

“Access to information is the public’s right,” the official said.

NDP Leader Jack Layton said it is “entirely appropriate” that interim Information Commissioner Suzanne Legault has given priority to probe a complaint about the handling of the access to request in Paradis’ office.

“We hope that it’s a speedy investigation so we can get to the bottom of this as soon as possible,” Layton said.

Liberal MP Siobhan Coady has asked Legault to widen her investigation to “all instances of Conservative interference and order the public release of all politically censored documents.”

The tough words from the Prime Minister’s office are cold comfort to critics who have long complained that the access to information process has worsened since Harper took power in 2006. They say high fees and long delays are choking the system, cutting off the flow of information.

“There has been a pattern of delay and obstruction with this government that should worry Canadians with regard to Access to information,” Layton said.

To back his claim, he cited a memo released to the Military Police Complaints Commission by the Justice Department in May with only a small portion blacked out while the other identical memo received last month by the NDP from National Defence was totally erased.

Layton said it is ironic that it was the Conservative Party that campaigned on a promise to make it easier to peek inside government, “but they have mostly abandoned the ideas that they were advancing at that time.”