And New Democrats are warning the majority government could be defeated if Conservative MPs fall asleep at the switch at any point during the marathon session.
The government has put itself in peril by cramming controversial changes to some 70 different laws into the 400-plus-page budget bill, NDP House leader Nathan Cullen warned Tuesday.
"If the votes go on for hours and hours, perhaps days, the government has to get every single vote right," Cullen said.
"It can't screw one up. They can't have members falling asleep, going home and not coming back for votes, missing votes. Because if they miss any of those votes, they put their own government in jeopardy."
Most of the non-budgetary measures in the bill — including overhauls to employment insurance, old age security, immigration, fisheries and environmental assessment laws — would not normally be considered matters of confidence.
But because they've been included as part of the budget bill, Cullen said the government's fate is now automatically on the line if any of the measures are not passed. He said the government should have listened to opposition parties, which have demanded that the bill be split up into more manageable chunks.
"By making it all into a budget implementation act, the government has put themselves at risk and painted themselves into a corner," he said.
"The government has dug themselves a hole. We asked them to stop digging, they went a got a bigger shovel."
The bill is currently being examined by the Commons finance committee, where New Democrat members are proposing amendments to eliminate or soften what they consider the most egregious elements. But Cullen said the government doesn't seem to want to change "a single period or a comma."
The bill is expected to return to the Commons next week, at which point Green party Leader Elizabeth May has vowed to move some 200 amendments. She has more latitude than other opposition parties to move substantive amendments at that stage because, as the lone Green MP, she is not a member of the finance committee.
The Liberals have promised to back May's amendments and move a host of their own, although they'll be limited primarily to amendments proposing to delete clauses from the bill. An insider said Liberals could move as many as 500 deletion amendments.
Cullen said the NDP also plans to move some 200 deletion amendments that will be complementary to May's.
It would take roughly 100 non-stop hours to get through recorded votes on 400 amendments. However, the Speaker may yet rule some amendments out of order or group a number of them together under one vote.
Interim Liberal Leader Bob Rae conceded the government will eventually use its majority to pass the bill but he said that doesn't mean opposition parties should "give up the ghost." He said they "have an obligation to fight this as hard as we can" to demonstrate the depth of public concern about the bill.
That said, Rae scoffed at the NDP's suggestion the government could be defeated.
"What I saw of Mr. Cullen he was promising today that he was going to be bringing down the government. I think he just makes himself look ridiculous when he says things like that."
Cullen likewise conceded the government will eventually "ram" the bill through. But he said opposition efforts to hold it up as long as possible are nevertheless vital because of what's at stake.
"Under the Harper Conservatives, accountability is under attack, the very institution of Parliament is under attack. This is an abuse of power and it's reckless."
The NDP conducted cross-country hearings of its own on the bill. Cullen said the party heard from thousands of Canadians who are concerned about the various measures in the bill and, more generally, about the government's determination to sneak such fundamental changes through, with little scrutiny, under the guise of budget implementation.
"Canadians said, 'This is wrong. Is there any way that you can stop this?'"
Government House leader Peter Van Loan countered that the bill is aimed at creating jobs, economic growth and long-term prosperity and maintained its swift passage is necessary given the fragility of the global economic recovery.
"It's time for the NDP to put Canada's economy first, instead of filibusters and other partisan procedural games," Van Loan said in an email statement from his office.
A spokesperson for Van Loan argued that the bill has already received the longest debate and committee examination of any budget bill in two decades.