The debate between Liberal Leader Robert Ghiz and Tory Leader Olive Crane had been planned for Sept. 21, but Crane said she wouldn't take part unless the leaders of the province's three other parties were included.
CBC spokesman Jeff Keay says you can't have a debate with just one leader, so the debate won't proceed.
He says the decision to exclude the New Democrats, Greens and Island party was made because the Liberals and Tories were the only two parties represented in the legislature.
Keay says the debate was only one event and the positions of all the parties are being reported throughout the campaign.
All five leaders will be part of a televised debate on Sept. 22, hosted by the Charlottetown Guardian newspaper and Eastlink cable television.