Liberal Leader Michael Ignatieff continued to pressure Prime Minister Stephen Harper for a one-on-one debate on Friday, issuing an open letter demanding the Conservative leader live up to his promise to square off against the Liberal leader.

"As you stated, there are only two people who can be Prime Minister after May 2nd: you or me," reads Ignatieff's letter, posted on the Liberal's website Friday morning.

"Canadians truly deserve to see us go face to face in a contest of ideas, values and very different visions for our country. That is what democracy is all about."

Ignatieff went on to say he was disappointed by Harper's about-face, and urged him to live up to his own challenge for a policy debate between the two leading parties.

"I will meet you at the time and place of your choosing. There is no need for complicated or convoluted debate formats. Just two podiums – and you and me. A true, honest-to-goodness battle of ideas and visions," Ignatieff wrote.

Several news organizations have stepped up in recent days to offer to host the debate. The idea has galvanized support online and has taken over the political conversation on social networks sites like Twitter.

Harper has stepped away from the possibility of a one-on-one debate after originally raising the idea on Wednesday.

He first raised the issue after Green Party Leader Elizabeth May was excluded from an upcoming televised leader's debate. Harper said he was open to various forms of debate including a face-off between himself and Ignatieff.

During a campaign stop in Dieppe, N.B., on Friday, Harper said he would leave the format up to the broadcast consortium that was organizing the debate and was not open to holding more than one debate during the five-week campaign.

"When I was asked about this our position was that we were open to a whole range of debate formats and that we would accept the judgment of the networks in the end," Harper said.

"We didn't get the preference that we want. If other parties had wanted a different preference that what they got they should have said so when we were having those conversations."

Meanwhile, NDP Leader Jack Layton accused Ignatieff of using the proposed two-party debate to sideline other party leaders in the national conversation.

"I think Mr. Ignatieff is showing he is not a true democrat, that he is trying to exclude people from the national discussion that have every right to be there," Layton said during a campaign stop in Sudbury, Ont.

Ignatieff has said he wants to participate in an all-leaders debate, which would include Layton, Bloc Leader Gilles Duceppe and May, as well as a one-on-one debate between himself and Harper.

"Canadians deserve this chance to see the different visions of leadership between the only two people who can become prime minister of this country at the end of this election," he wrote.

Lost amid the fight for a Liberal-Conservative square dance is the Green Party leader's own battle to be included in all-party debates.

May managed to get into the 2008 debates thanks to an agreement from the other party leaders, but remains shut out this time around by the consortium of broadcasters, of which CTV is a member.

May began a push for a judicial review of the situation, and the Greens have hired a lawyer to argue their case. The consortium has maintained that only parties with seats in Parliament can take part.

The English debate is set for April 12 while the French debate will occur two days later.

With files from The Canadian Press