Saskatchewan Premier Lorne Calvert has climbed on the same soapbox as his Newfoundland counterpart, saying the federal Conservatives have broken a key budgetary promise to his province and may lose support as a result.

Newfoundland Premier Danny Williams has taken out national newspaper ads slamming the government and has criticizing the budget in numerous interviews, calling on Newfoundlanders to vote against the Tories in the next election.

During an appearance on CTV's Question Period on Sunday, Calvert said he's equally angry, claiming Prime Minister Stephen Harper simply didn't keep his promise to fully exclude non-renewable natural resources from the formula used to calculate equalization payments to the provinces.

Harper's promise, made during the last election, would have meant hundreds of millions more in funding for the Saskatchewan.

Instead, the Conservatives' allowed for the option of removing resource revenues, but capped the amount of money paid out to provinces under the equalization program.

Much like Williams' current campaign, Calvert said he is working to convince people in Saskatchewan that the Conservatives -- a party that holds 12 of 14 federal seats in the province -- have let the province down.

"The people of both of our provinces have been promised by this prime minister and this Conservative government that when it comes to the calculation of equalization we would see 100 per cent of our non-renewable natural resources revenues excluded, so we would stop sending these revenues from the province to other parts of Canada," Calvert told CTV's Craig Oliver, co-host of Question Period.

"That was a promise made, not just in one election but two elections. It was made not just to Newfoundland and Labrador and Nova Scotia but also to Saskatchewan, Alberta, British Columbia, and the promise was broken."

In new radio ads running in Saskatchewan however, the Conservatives claim the new budget does keep the pledge to remove natural resources revenue, and that it delivers $878 million in new funding to the province and provides the largest per-capita investment of any province.

But Calvert said he is taking out ads of his own and is spreading his own message through a public awareness campaign. He warned the Conservatives could lose support over the issue.

"The fact of the matter is some of those (Conservative) seats were won on the promise to be fair to Saskatchewan when it comes to our non-renewable natural resources," Calvert said.

"Of course I'm a strong New Democrat, Danny Williams is a strong Progressive Conservative, but on this, I'll tell you, this is a promise made to the people."

Calvert said people from all political stripes in Saskatchewan, and across Canada, have united in calling on Harper to do more to keep his promise to exclude non-renewable natural resource revenue from the equalization formula.

Calvert also said he, along with every "Martha and Henry" in Saskatchewan, believes the new equalization measures mean the province's resource revenues are being used by the federal government to provide tax cuts to Quebec, and thereby buy votes in the key province.