OTTAWA - The House of Commons has voted in support of a bill to implement the Conservative government's budget amid warnings that could tighten the political collars on almost 20 Tory MPs.

The bill passed second reading 164-104 on Tuesday with the support of the Bloc Quebecois.

That means it's almost certain to pass third and final reading by June, assuring what some provincial premiers claim is the demise of a Conservative election promise to keep oil and gas resource revenues out of the equalization formula.

Under the budget legislation, Nova Scotia and Newfoundland and Labrador must choose between their hard-won offshore-resource deals and a new equalization formula that could cost them $1 billion each over the long term.

Saskatchewan, meanwhile, will see revenues from its burgeoning oil and gas industry clawed back back through reduced equalization payments. The province's equalization payments are slated to drop to zero next year because of a cap imposed in the equalization formula.

Premiers from all three provinces have called out their Tory MPs for what they see as the blatant breaking of one of Stephen Harper's 2006 campaign promises.

However, the MPs, led by Foreign Affairs Minister Peter MacKay -- Harper's political minister for Atlantic Canada -- stood by their government and voted for the bill.

The NDP ensured there would be a recorded vote on second reading so that no Conservatives could duck responsibility for supporting the government legislation.

The controversy revolves around a letter Harper sent to Newfoundland Premier Danny Williams on Jan. 4, 2006 in mid-campaign.

"We will remove non-renewable natural resource revenue from the equalization formula to encourage the development of economic growth in non-renewable resource sectors across Canada,'' Harper wrote.

"The Conservative government will ensure that no province is adversely affected from changes to the equalization formula.''

The government argues that's precisely what the budget delivers, with no province worse off under the new rules than under the old ones.

But some provinces say otherwise, and at least 18 Conservative MPs -- 12 from Saskatchewan and three each from the two Atlantic provinces -- were publicly admonished to vote against the budget bill.

While Williams' fiery public campaign has gathered the most exposure, the larger Saskatchewan Tory caucus is also under pressure.

Last July, the group felt compelled to warn Harper in a letter that "anything less than substantial compliance with our commitment (on resource revenues) will cause no end of political difficulty during the next federal election.''

The letter from MP Brian Fitzpatrick, chair of the Saskatchewan Conservative caucus, said newspaper coverage in the province had made it "abundantly clear'' there was very little "wiggle room'' for the government.

Before the vote, MacKay said Tory MPs would be happy to back the budget bill, but wouldn't be forced to vote that way.

"We won't throw a member out of caucus for voting his conscience,'' he said. "There will be no whipping, flipping, hiring or firing on budget votes as we saw with the Liberal government.''

Saskatchewan Liberal MP Ralph Goodale predicted the vote will hurt some Conservative MPs' re-election prospects.

"The promise was clear. That they broke the promise is clear,'' said Goodale. "That they expect political fallout is absolutely clear. Saskatchewan people feel they've been lied to.''