OTTAWA - The budget bill that ruptured the Tory family and left three provinces screaming betrayal is now threatening to turn into a test of Liberal Leader Stephane Dion's leadership.

Dion and his Grit colleagues in the Senate are at odds over whether the unelected upper chamber must accept the contentious budget implementation bill now that it's been approved by the House of Commons.

Dion was unequivocal Wednesday: senators have no choice but to accept the bill no matter how little they like it.

"It's even the law," Dion said of the Senate's responsibility not to block budget bills.

He suggested there's little point in the Liberal-dominated Senate amending the bill, as some senators have suggested, since it would simply be sent back to the Commons where the Grits do not command a majority.

"We have no possibility to impose any amendment in the House and everybody knows that because we don't have the numbers," Dion said.

"At the end of the day, the budget will be the budget that the House has voted yesterday, despite the fact that it's a bad budget."

But Liberal senators insisted they're perfectly within their constitutional rights to amend or even defeat the bill, which is vehemently opposed by Nova Scotia, Newfoundland, and Saskatchewan. The three provinces contend the budget reneges on a Tory promise to allow them to reap the full benefit of their natural resource wealth, without clawback of their equalization payments.

Senator Terry Mercer said senators do have options in dealing with the bill.

"I think you'll find that senators from Nova Scotia, such as myself, from Newfoundland and Labrador, and probably from Saskatchewan, will all vote against it and I don't think we'll be alone," Mercer said.

"If we care to mount a full-fledged campaign with our colleagues, I think we can defeat this bill."

Celine Hervieux-Payette, Liberal leader in the Senate, said there is no law or convention requiring the red chamber to rubber-stamp budget implementation bills. On the contrary, she said the Senate has a duty to respond to the concerns of provinces.

"We have a special mandate to represent a region and represent minorities and this is what we're going to do. It's really within our mandate."

Hervieux-Payette noted that there is precedence for the Senate amending and even defeating budget implementation legislation. She pointed to one precedent set in 1993.

At that time, the Senate, dominated by Tories, first tried to amend a budget implementation bill to delete a proposed merger of the Canada Council with the Social Sciences and Humanities Research Council. The Tory government of Brian Mulroney rejected the amendment so the Senate ultimately defeated the bill.

Mercer pointed out that the Senate is not considered a confidence chamber and thus, unlike the Commons, it can defeat money bills without provoking an election. He said he's already warned Dion that he and other Atlantic Canadian senators won't support the bill, regardless of the leader's view on the matter.

"I can't walk down the streets of north-end Halifax where I grew up and look people in the eye if I support this," Mercer said.

The bill, passed by the Commons on Tuesday, will head to the Senate's finance committee for examination next week. Rodney MacDonald and Danny Williams, the Tory premiers of Nova Scotia and Newfoundland, have already asked to testify on the bill and Saskatchewan's Lorne Calvert is expected to follow suit.

Hervieux-Payette said the Senate will not be rushed and dismissed the Harper government's contention that more than $4 billion in funding for things like climate change, patient wait times and post-secondary education will be lost if the bill isn't enacted by the end of the month.

"I've been told by others that this is totally false, the money will not be lost," she said.