Kevin Page has given officials in 56 departments and agencies until Wednesday to provide information about cuts and savings in the federal budget.
On Sunday, he told CTV's Question Period he'll take his fight for information to court if need be.
"The information we're asking for is the information that's actually fundamental for MPs to do their jobs," Page said.
"If we cannot get this information from deputy ministers, we may have to seek this kind of clarity. But it was never our first option.
"We would go to court if we have to."
But the Conservative cabinet minister in charge of the cuts wants Page to butt out.
Treasury Board President Tony Clement told CBC Radio's The House this weekend that Page is operating outside his mandate — an argument he says he's willing to make before the courts.
"When you look at the words in his mandate — the finances, the estimates and the trends in the national economy — it's not about money not spent, it's about money spent," Clement told CBC.
Clement says it's the Parliamentary Budget Officer's job to look at what the government spends money on — not what it doesn't.
"There's lots of work for him to do inside his mandate and he should stick to that," he said.
He said the government is accountable to Parliament through estimates, quarterly departmental reports and public accounts documents.
However, Page told CTV it's his office's job to look at both spending and cuts.
"We think we're very clearly within our mandate. And it's very important to look at austerity," Page said.
"Sometimes what you don't spend money on is just as important as what you spend money on."
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