Ousted as leader of Turkey's main opposition, Ozgur Ozel on Friday resigned from the CHP alongside 90 other lawmakers, setting up his own party to lead the fight against President Recep Tayyip Erdogan.

In a video broadcast by Turkish media and posted on X, Ozel could be seen sitting at his desk, flanked by a large Turkish flag, signing both his resignation papers and the founding documents for "Yeni Parti", or "New Party".

"May it be beneficial to our country, our nation, our party, and all of us," he said.

The paperwork to set up Yeni Parti will be presented at the interior ministry around noon, officials said.

With 91 lawmakers, it will be the second largest party in Turkey's 600-seat parliament after Erdogan's ruling AKP, which holds 277 seats.

Until now, the CHP had been the second largest with 135 lawmakers.

But with the resignations, that number drops to 44, leaving it in fourth place after the pro-Kurdish opposition DEM party, which has 56 seats.

Ozel's move comes two months after a court ruling removed him as CHP leader and brought back his defeated predecessor Kemal Kilicdaroglu, sparking widespread anger within Turkey's oldest political party.

Although Ozel appealed against the ruling, procedural delays meant the paperwork did not reach the Supreme Court until just hours before it broke for the summer recess, triggering his move to set up a new party.

- 'A shirt of fire' -

The Ankara court ruling annulled the CHP's 2023 leadership election over allegations of vote-buying in a move widely seen as a political manoeuvre to quash Erdogan's opponents, raising concerns about democracy and the rule of law in Turkey.

In his last speech to lawmakers at the CHP's weekly parliamentary group meeting on Tuesday, Ozel said Turkey stood at "a historic crossroads".

"The new party we are about to establish will become the main opposition force in the Grand National Assembly (parliament) by a wide margin," he told lawmakers, who gave him a standing ovation.

"In politics, we do not give up on our beliefs; instead, we all take on a difficult and risky burden for the country's sake," he said, using a Turkish idiom about "putting on a shirt of fire".

Within months of Ozel's election as CHP leader, the troubled party's fortunes appeared to be transformed, with it winning a huge victory in local elections, trouncing Erdogan's AKP.

Since then, it has been battling a growing wave of judicial pressure, with hundreds of party officials arrested on graft allegations, including Istanbul mayor Ekrem Imamoglu, widely seen as one of the only politicians capable of defeating Erdogan at the ballot box.

To date, at least 27 CHP mayors are behind bars.