UNP MP Wasantha Senanayake has been removed from party membership, party General Secretary Akila Viraj Kariyawasam said.
He said the party would make a formal request to the President to remove Senanayake from his ministerial portfolio.
Senanayake is currently the State Minister of Foreign Affairs.
Action has been taken against the UNP MP for acting in violation of party discipline.
Senanayake, who switched sides multiple times during the constitutional crisis last year, is now expected to support SLPP candidate Gotabhaya Rajapaksa.