Environment Minister Peter Kent, Natural Resources Minister Joe Oliver and Fisheries Minister Keith Ashfield popped up at the subcommittee hearing Thursday morning, without advance public notice.
They stayed for just over an hour, delivering prepared statements and taking MPs' questions.
It was the subcommittee's first hearing into the parts of the bill that will overhaul environmental assessments and change surveillance of fisheries.
Opposition members complained they were given little opportunity to grill the ministers over fundamental changes to Canada's environmental framework, and accused the Conservatives of trying to stifle debate.
The Conservatives have loaded the budget bill with dozens of major changes to the way government works, saying they are lumping them all together because they want to get the legislation passed quickly.
"Whoever took the decision to schedule our three ministers for one hour was not acting on the authority of the subcommittee," said Liberal MP Kirsty Duncan.
"I feel it was presumptuous, it was undemocratic, and I think it's farcical to have three ministers appear at the same time for a total of one hour.
"Taking away time for opening statements and friendly questions from the government, that gives about 20 minutes for the opposition parties to ask questions of three different ministers on 150 pages devoted to the environment on this omnibus bill."
Duncan tried to make the most of her time by asking short, pointed questions and requesting that detailed, written answers be tabled with the committee later.
Kent said he would be pleased to appear before the subcommittee again.
And his spokesman said there was nothing nefarious about the sudden appearance of the ministers, since Kent had signalled earlier this week that he would appear soon.
Spokesman Adam Sweet said the hearing was televised, and that New Democrat MP Peter Julian was told in advance the ministers would be there.
Meanwhile, more than 130 scientists and other professionals at Fisheries and Oceans were told Thursday their jobs were at risk, their union said. That's in addition to 200 others who were given similar notices in December.
The pending cuts mean that facilities such as the Experimental Lakes Area environmental program near Kenora, Ont., will lose their expertise to track freshwater ecosystem fluctuations, said Gary Corbett, president of the Professional Institute of the Public Service of Canada.
"The government is eliminating programs that have generated world-renowned studies of freshwater ecosystems as well as impacting work to monitor Arctic contaminants, dioxins and other pollutants," he said.
Corbett added that the cuts together with the changes in the budget bill throw the sustainability of Canada's environment into question.
The trio of ministers at committee repeatedly denied that the changes would weaken environmental oversight. Rather, they said the regime would be more efficient, and new enforcement measures would give legislation more teeth.
The budget bill has prompted an outcry from opposition parties, who say the legislation is packed with so many poorly defined changes that it poses more questions than it answers — not just on the environment, but also on employment insurance and old age security.
Ministers have said changes to the Fisheries Act as well as to employment insurance will be fleshed out later through regulations, which are not subject to full parliamentary debate.
"Why won't they table their plans in this House for everyone to see," New Democrat MP Libby Davies asked in the Commons.
Interim Liberal Leader Bob Rae complained that the budget bill has a "complete lack of clarity" on changes to employment insurance. He said it is not reasonable to ask Parliament to approve changes they have not yet seen.
But Heritage Minister James Moore responded that the government's plan for jobs and growth has received extensive debate.
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