OTTAWA — Liberal Leader Michael Ignatieff is threatening to introduce a motion of non-confidence in the Conservative government as early as next week.

Lashing out at the minority Conservatives over unemployment insurance, isotopes and the deficit, Ignatieff said his party “will make a serene and clear decision” by midweek about whether it wants to topple the Tories.

The government’s second “report card” on the federal budget’s economic stimulus package is due sometime in June. That could be the catalyst for a non-confidence vote.

“I’m trying to make Parliament work with a government that every day is displaying more flagrant examples of incompetence,” Ignatieff told reporters. He said the Tories had “no plan” to deal with the isotope shortage and were posting staggering deficit numbers.

TD Bank yesterday said the deficit could be more than $172 billion over the next five years.

“The public finances of the country are not under control,” Ignatieff said.

Even if they wished to, the Liberals could not take down the Conservatives by themselves; they need support from both other opposition parties. Ignatieff said he had not consulted them.

Bloc Quebecois Leader Gilles Duceppe was unimpressed.

“Ignatieff has been switching positions since he became leader,” Duceppe said. “He gets up in the House and says ‘How can we have confidence in this government?’ and then when it comes time to vote, he switches positions and votes with the government.”

NDP House leader Libby Davies was non-committal about her party’s potential support. “We’re not going to say in advance without knowing what the motion is.”

The economic report card is due before Parliament rises for the summer. The Liberals will get the chance to move a confidence motion on an opposition day, which must be held by June 23.

Dimitri Soudas, a spokesman for Prime Minister Stephen Harper, said no date for releasing the report card has been set.

“Mr. Ignatieff’s recent threats for an election, they smell like nothing more than political opportunism and it’s unfortunate that he would want to play politics during a time of recession,” Soudas added.