Donald Trump filed a lawsuit on Wednesday against his former personal lawyer and fixer Michael Cohen, a likely star witness in the criminal case facing the former US president in New York.

The suit, filed in a US District Court in Florida, seeks $500 million from Cohen over his alleged breach of attorney-client privileges and a confidentiality agreement.

Cohen was among the witnesses who testified before the grand jury that ultimately indicted Trump, making him the first former or sitting US president to face criminal charges.

He has been charged with 34 felony counts of falsifying business records in connection with a hush money payment to porn star Stormy Daniels.

Cohen says he arranged the $130,000 payment in exchange for her silence about a tryst Daniels says she had with Trump in 2006.

Trump pleaded not guilty to the charges in a Manhattan court on April 4.

In his lawsuit, Trump accuses Cohen of "spreading falsehoods" about him and claimed to have suffered "vast reputational harm."

"Such continuous and escalating improper conduct by (Cohen) has reached a proverbial crescendo and has left (Trump) with no alternative but to seek legal redress," the suit said.

Trump is seeking a jury trial and compensatory and punitive damages of more than $500 million.

The 76-year-old former real estate tycoon has been embroiled in scores of lawsuits over the past decades and has a long history of attacking his opponents in court.

Cohen, 56, is expected to be a star witness for the prosecution if the criminal case against Trump in Manhattan ever comes to trial.

He has acknowledged paying Daniels on Trump's behalf and was sentenced to three years in prison for various crimes, including the hush-money case and tax evasion.

Trump has denied any wrongdoing and claims he is the victim of a political "witch hunt" by the Manhattan district attorney, a Democrat, intended to derail his 2024 White House campaign.