BANGKOK (AP) — The embattled head of the Move Forward party, which finished first in Thailand’s general election in May but was denied power by Parliament, announced his resignation on Friday as its chief so the party can appoint a new member to serve as Parliament’s opposition leader.

The constitution requires the leader of the opposition to be an elected lawmaker and a leader of a political party. Pita Limjaroenrat, Move Forward’s 43-year-old leader, is currently suspended from his duties as a member of Parliament pending a court ruling on whether he violated election law.

Pita wrote on social media that he decided to resign as Move Forward’s leader because he has to comply with the court’s order of suspension, so he cannot perform his duties as a lawmaker and cannot be an opposition leader “in the foreseeable future.”

“The role of opposition leader is greatly important to the parliamentary system, and is supposed to be held by the leader of the main opposition party in Parliament, which currently is Move Forward,” he said. “The opposition leader is like the prow of a ship that directs the opposition’s performance in Parliament, performs checks and balances in the government and pushes for agendas of change that are missing from the government’s policy.”

He later told reporters the party will select its new leaders on Sept. 23.

As Pita was seeking Parliament’s support in July to be named prime minister, the Constitutional Court suspended him from holding his seat in the House of Representatives pending its ruling on whether he violated the law by running for office while holding shares in a media company, a charge he has denied. The violation is punishable by up to three years in prison and a fine of up to 60,000 baht ($1,720). His party can be fined up to 100,000 baht ($2,865).

The Constitutional Court has yet to set a ruling date for Pita’s media shares case. In late August, it allowed him a 30-day extension to prepare his defense.

The progressive Move Forward party won the most votes in May’s elections but was blocked from taking power by the conservative members of the Senate, who, though not elected, vote jointly with the Lower House to approve a new prime minister. The Senate was given that power under a constitution promulgated under military rule that was meant to maintain conservative influence in government.

The Pheu Thai party, which finished second in the May election, was able to form a coalition acceptable to the senators, and had one of its candidates, Srettha Thavisin, confirmed as prime minister. Srettha’s coalition embraced military-supported parties that include members linked to a 2014 coup that ousted a previous Pheu Thai government.

Move Forward’s bid to lead the opposition was complicated not only by Pita’s suspension, but also because one of its members is currently serving as the first deputy house speaker. Padipat Suntiphada was selected for the post while Move Forward was still seeking to form a government, but the rules bar members of parties leading the opposition from holding speakers’ positions in the House.

Chaithawat Tulathon, the party’s secretary-general, said Padipat’s status will be determined by the party’s new leaders.