The United National Party will move a no-confidence motion against Deputy Speaker Thilanga Sumathipala at the next Parliamentary session.
"Sumathipala has acted in a capricious,arbitrary and unfair manner without acting independently in the current no faith motion," Minister Navin Dissanayake said.
Sumathipala, a close ally of President Maithripala Sirisena, is a member of the Sri Lanka Freedom Party.
Sources within the UNP said Sumathipala played a key role as a 'middleman' between the SLFP and the Joint Opposition on the no-confidence motion against Prime Minister Ranil Wickremesinghe.