Conservative Leader Stephen Harper says he's open to a one-on-one debate with Michael Ignatieff, which prompted the Liberal leader to throw down the gauntlet on Twitter: "Any time, any place."

"A one-on-one debate will show Canadians the clear choice on May 2nd: the Harper regime or a Liberal government," Ignatieff said Wednesday on his official Twitter account.

In turn, Harper, on his official Twitter account, replied: "curiously, my team proposed 1:1 to TV consortium today; however, your team did not speak up."

Ignatieff first raised the idea of a one-on-debate with Harper on Tuesday evening in response to the broadcast consortium's decision to exclude Green Party Leader Elizabeth May from the televised leaders' debates. He said he believes May should be allowed to participate, but added he wanted to debate Harper face-to-face.

Earlier Wednesday, Harper said he was willing to take on Ignatieff, but said the decision was ultimately up to the broadcast consortium.

"We're open to any number of possibilities. We could have a traditional debate of Parliamentary leaders, we could have a debate that includes Miss May in such a format, we could have a debate that includes every party that's on the ballot," Harper said.

"We could also have a debate between Mr. Ignatieff and myself, since, after all, the real choice in this election is a choice between a Conservative government or an Ignatieff-led government that all of these other parties will support," he said during an Ontario campaign stop.

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"The networks will ultimately have to make a decision that serves the public interest and we will insist that it treat ourselves and all parties fairly."

Meanwhile, NDP Leader Jack Layton also joined the Twitter fray, telling Harper he remembered the debates in the 2008 election.

"Don't blame you for not wanting to face me again," Layton quipped.

Layton's party also issued a statement questioning what Ignatieff and Harper would debate, citing the leaders' similar positions on the Harmonized Sales Tax, Afghanistan and funding for the arts.

Bloc Leader Gilles Duceppe called the idea of a one-on-one debate an attack on democracy aimed at excluding Quebec.

Brian Topp, one of Layton's strategists, suggested on Twitter that several one-on-one debates with all the leaders could be held in different parts of the country.

"Ignatieff wants 1x1 debate with Harper. Maybe in Toronto. Then how about Layton vs. Harper in Vanc/prairies/n.ont+Quebec. Say, 4 1x1s?" Topp replied.

As for May participating in the debate, both the Liberals and the NDP have said they are open to the idea, despite the broadcast consortium's decision only to include leaders of the four parties who are currently represented in the House of Commons.

Harper talks taxes in Ontario

Earlier Wednesday, Harper visited an industrial manufacturer to announce the Conservatives would extend the accelerated capital cost allowance that allows businesses to write off the cost of new equipment faster. The measure was in the budget last week that died when the government fell.

Speaking at an event with local candidates in Brampton, Ont., Harper stressed his party's lower-tax plan for businesses.

He also announced an extension of accelerated business write-offs for capital investments. He said this would help Canadian companies invest in machinery and equipment to raise productivity and create jobs.

"Our plan is designed to complete Canada’s economic recovery and support job creation," he said. "It will achieve these goals through incentives for protecting jobs and creating jobs by keeping taxes low."

Harper said that according to the Canadian Manufacturers and Exporters, the accelerated capital cost allowance boosted investment by more than 11 per cent between 2006 and 2009.

"If you want people to invest, you need to make it easy for them," he said. "Lowering taxes on investments will create and protect jobs for Canadians."

He also mentioned an $80 million increase in funding to increase collaboration between manufacturers and colleges — the Industrial Research Assistance Program.