The UNP said it also decided to boycott the meeting convened by Prime Minister Mahinda Rajapaksa for all MPs of the dissolved Parliament.
The SJB and the JVP have already stated that they will not attend the Prime Minister's meeting at Temple Trees.
The UNP was initially in favour of attending the meeting. Informed party sources said the UNP changed its plans following the strong position adopted by the SJB and the JVP.
Issuing a statement, the party said the government would not facilitate a meaningful dialogue by convening a meeting of this nature.