The Conservatives have taken aim again at one of their budgetary foes, accusing parliamentary budget officer Kevin Page of overstepping his mandate.

On Monday, Page released a legal opinion that supported his view he was entitled to all financial and economic data the departments have, as long as they aren't protected for privacy or cabinet confidence reasons.

Most departments — 64 out of 84 — refuse to release the data Page says he needs to do his job, and which opposition MPs requested before they voted on the federal budget.

"What do [Conservative MPs] have against transparency? What do they have against accountability?" NDP Leader Tom Mulcair said.

Foreign Affairs Minister John Baird says it was his government that brought in the legislation that created Page's watchdog role. At the time, Baird was president of the Treasury Board, the minister in charge of the Federal Accountability Act.

"I'd have to say with great respect, I believe that from time to time and on occasion the parliamentary budget officer has overstepped [his] mandate," Baird said Tuesday.

Asked for examples of when Page overstepped his mandate, a government spokeswoman didn't respond.

Criticism sends 'strong message'

The government has criticized Page in the past, including for his estimated cost of the F-35 fighter jets. A report by Auditor General Michael Ferguson last April supported Page's estimates rather than the government's. Earlier this year, Finance Minister Jim Flaherty criticized Page for his assessment of Old Age Security being sustainable following changes to health-care funding.

Speaking after question period, Mulcair said Baird's criticism looked pre-planned.

"He had his document in front of him, he was reading. This is something sent in by the Prime Minister's Office, so it's a warning that Kevin Page has made the ultimate mistake. He doesn't tell the Conservatives what they want to hear. And he actually wants to be able to say the truth to the Canadian population," Mulcair said.

"Right now the Conservatives are sending another strong message. You're not allowed to disagree with them and, by the way, even if you have a mandate under the law to give information to parliamentarians and to the Canadian public, you can be starved of that information, even if it's a clear infraction of the law."