The Supreme Court's Election Cases Division on Thursday disqualified Pheu Thai MP Karun Hosakul and ordered the Election Commission to hold a by-election in Bangkok's constituency 12 to replace him.
The court also imposed a five-year electoral rights ban on Mr Karun.
On June 20, 2012 the EC decided by a majority to red-card Mr Karun after finding him guilty of making false accusations defaming rival candidate Taenkhun Jitt-itsara and the Democrat Party at campaign rallies in Don Muang area at Boon-Anant market on June 3, 2011 and Kosum Ruamjai market on June 12, 2011 during the lead-up to the July 2, 2011 general election.
These false accusations could have misled people to not vote for Mr Taenkhun in violation of section 57 of the law on the election of MPs and senators, the EC concluded.
The EC submitted its finding and recommendation to the Supreme Court's Election Cases Division on July 15, 2012, seeking a final order.
The court's ruling will be sent to the House of Representatives, the Prime Minister's Office and the EC for formal acknowledgement.