OTTAWA -- Prime Minister Stephen Harper will defend his budget this morning, after all three opposition parties have served notice they will reject the economic blueprint and trigger a spring election.

Harper is set to make remarks on Parliament Hill just before lunchtime, hoping to put his spin on the opposition parties' treatment of the budget. He'll then tie up some loose ends by attending a royal assent ceremony later this afternoon, bringing into law any lingering legislation that has passed through the House of Commons and the Senate.

The Tories released yet another attack ad today, accusing the opposition parties of imperilling the fragile economy by forcing an unnecessary election. Ottawa is rife with rumours that Harper would prefer to make the election call himself instead of waiting for the opposition parties to take him down through Commons procedures.

The Tories are facing accusations of contempt of Parliament, and have been dealing with a string of scandals.

But so far Harper has not made public any plans to contact the Governor General and ask for the dissolution of Parliament.

Both the budget and the accusations of contempt will give the opposition parties several chances to bring down the government over the coming days. A vote of non-confidence could come as late as Friday afternoon.

That's when the Liberals can ask Parliament to vote on whether the Harper government was in contempt by holding back information on the cost of crime bills, the cost of F35s, and the fiscal implications of corporate tax cuts.

It was the NDP that unleashed the latest round of election fever on Parliament Hill.

Within minutes of Finance Minister Jim Flaherty tabling his budget on Tuesday, NDP Leader Jack Layton said his party did not see enough in the document to warrant continued support of the Conservative government.

"Mr. Harper had an opportunity to address the needs of hard-working, middle-class Canadians and families and he missed that opportunity," the NDP leader told a throng of reporters. "He just doesn't get it."

Since the Liberals and the Bloc Quebecois had made their opposition to the budget clear from the get-go, the only chance the Tories had of salvaging their plan — and their hold on power — was the NDP.

The budget contained several nods in the New Democrats' direction.

It included a $300-million top-up to benefits for the poorest of poor seniors. It put $400 million into a one-year program to help homeowners make their houses more energy efficient. And it set aside $9 million a year to entice doctors and nurses to move to rural areas.

For the NDP, it was not enough. They had asked for $700 million for seniors, continual funding for the homeowners energy program, and plans to train new doctors and nurses.

They had also asked for assurances that the federal government would work toward an expansion of the Canada Pension Plan. And they wanted Ottawa to remove the federal tax from home heating. The budget ignored those requests.