Yesterday's court mediation session collapsed after the red and yellow leaders refused to drop any of the libel cases they had filed against each other.
The three red-shirt leaders - Veera Musigapong, Jatuporn Promphan and Natthawut Saikua - have filed seven lawsuits charging yellow-shirt leader Sondhi Limthongkul for defamation.
Sondhi, meanwhile, has filed two counter-suits against the three.
Veera and Natthawut, under remand on terrorism charges, were present at the mediation session, while lawyers represented Jatuporn and Sondhi.
In a separate development, Pheu Thai Party spokesman Prompong Nopparit filed a defamation lawsuit against Democrat chief adviser Chuan Leekpai.
"Chuan, despite his seniority from having served two terms as prime minister, has made irresponsible remarks to tarnish my reputation," he said.
Prompong added that he wanted to salvage his credibility as spokesman after Chuan labelled him a "daily liar".
Chuan allegedly made these remarks as a rebuttal after Prompong told reporters that a senior Democrat, whose first initial is C, lobbied for an aspiring candidate from the New Politics Party not to enter the race for the by-election in Bangkok Constituency 6.
The Criminal Court will rule on August 26 as to whether it will accept the case for judicial review.