OTTAWA -- The RCMP repeatedly stonewalled media inquiries for months about the price tag for destroying the federal long gun registry data, even though the federal police force had a full cost estimate in hand.

The Mounties had a detailed breakdown more than a year ago that showed fulfilling the long-time Conservative promise to kill the registry would cost about $1 million.

A PowerPoint presentation laying out the plan and its costs was provided to The Canadian Press under an Access to Information request following an 11-month delay.

In the meantime, RCMP officials refused to answer direct questions about whether any such costing had been done, saying only that any spending related to the registry's destruction would come out of the force's own budget.

NDP justice critic Francoise Boivin says the RCMP's handling of the file calls into question whether its communications can be trusted on bigger issues -- including the current Senate investigation of improper expense claims.

"They should have volunteered this (information) showing how much it cost. Instead, by stonewalling they make us think the worst," Boivin said in an interview.

There seems to be "some type of unwritten law of silence" across the Harper government, but secrecy on routine matters by the Mounties is particularly damaging, Boivin said.

"It's sad when it comes from an agency like the RCMP that is there to uphold the law. They're supposed to be leaders in this society on how to behave well," she said.

"How can we trust them with bigger files? Can we trust that they will do the inquiry well on the Senate, on any other thing? It's understandable that we have doubts."

The RCMP did not respond to a request for comment but a spokesman for Public Safety Minister Steven Blaney reiterated in an emailed response that the data destruction "involved no additional costs to the taxpayers."

When asked if the money spent on the data destruction was coming from other RCMP priorities, Jean-Christophe de Le Rue responded in another email that "I don't think we are hiding anything here. Let me be clear: money allocated for administrative work cannot be spent on programming."

The government says it can't provide a hard figure on the actual cost of the destruction. Because the funding came out of the RCMP's existing budget, it didn't keep records.

The initial estimate forecast $425,000 on changes to the firearms information system and online databases, $300,000 to "manually review all paper files and purge (destroy) any records on non-restricted registration," $50,000 to change policy manuals and forms, and $150,000 on communications materials.

The Harper government, which came to power in 2006 with a promise to repeal the long-gun registry, has long played fast and loose with financial numbers surrounding the program.

Government ministers and Conservative MPs repeatedly cited the long-gun registry's lifetime cost as $2 billion, a total favoured by sport shooting lobbyists but refuted by auditor general reports and the Canadian Firearms Centre's own annual accounting.

Internal government figures, released to the Toronto Star through an access request only after the registry was finally voted out of existence in February 2012, showed the actual savings of killing the registry totalled about $2 million annually.

The file has always been politically sensitive for the government, and an Access to Information request on data destruction by The Canadian Press was flagged by the RCMP to the public safety minister's office.

An email dated Nov. 9, 2012, included the access question, noted it was the only "firearms-related" ATIP that week and stated the "catalyst could be the recent inquiries (Oct. 16, 17, 22) to RCMP media relations" by a Canadian Press reporter named in the email.

The email appears to have been sent to at least 116 individuals within government.