Prime Minister Stephen Harper responds to a question in the House of Commons in Ottawa on Wednesday. (Sean Kilpatrick/Canadian Press)

Prime Minister Stephen Harper suggested Wednesday that he would be willing to go to the polls over Liberal calls for changes to the employment insurance system.

Harper made the veiled threat during a heated exchange with Liberal Leader Michael Ignatieff, whose party has spent the past week calling for reforms to the program.

Ignatieff and Liberal MPs are urging the government to lower the minimum threshold to claim EI to 360 hours and make it a national standard.

A day after he was formally named Liberal leader in early May, Ignatieff said his party would be willing to push for an election if the changes are not made. He has called for Harper to deliver concrete reforms before Parliament breaks in June.

Harper said the Liberal proposal is equivalent to a massive increase in payroll taxes that business and workers can't tolerate and warned he's willing to "take on" the Liberals over the issue.

"If that leader wants to go out and tell Canadians that he thinks they should pay higher payroll taxes so that people can work 45 days and then collect EI for a year, every single year in every single region of the country, well, we're ready to take him on," he said.

Tories launch attack ads

The suggestion comes as the Conservatives launched a new television and internet campaign against Ignatieff.

The ads depict Ignatieff as an "arrogant elitist" who only plans to remain in Canada if he becomes prime minister.

Three English TV commercials all begin the same way, asking viewers why Ignatieff, who has lived outside of Canada for 34 years, returned after being away so long.

"Is he interested in people like you? No, instead he brags that he's horribly arrogant, a cosmopolitan, and while away, the only thing he missed about Canada was Algonquin Park," a narrator says.

"With such a focus on his own success, he's not in it for you or for Canada. He's just in it for himself."

The French-language commercials point out Ignatieff speaks French with a Parisian accent, rather than a Quebec accent.

Two senior Conservative spokesmen unveiled the campaign Wednesday on condition they not be named. They said staff had pored over decades worth of statements Ignatieff has made in books, magazines, TV shows and interviews and conducted market research with "real Canadians."

The Conservatives have not said how much the ads cost.

Ignatieff said the ads are designed to divert the public's attention from the real issues affecting Canadians, such as the economy.

"We're in the middle of a serious economic crisis," he said. "This government needs to grow up and do its job properly."

"I'm not going to attack Mr. Harper personally. I don't expect he should attack me."

With files from The Canadian Press