Justice Arthur Engoron on Monday ordered Mr Trump pay a fine of $10,000 (£7,850) per day until he complies.

New York Attorney General Letitia James had asked the court to hold Mr Trump in contempt after he missed a March deadline to present certain documents.

Mr Trump's lawyer said she would appeal the ruling.

"Everything that your honour and the attorney general said that we haven't done - we have done," attorney Alina Habba said in court.

After a "very diligent" search, there were simply no more relevant documents to provide, she said.

Ms James, a Democrat, opened a civil inquiry in 2019 into claims that - before he took office - Mr Trump, a Republican, had inflated the value of his assets to banks when seeking loans.

Costs rising for Donald Trump

The stakes have been raised in this year's long legal wrangle between Donald Trump and New York's dogged state attorney general.

Letitia James has accused the former president of stonewalling - and now she's successfully made it that much more costly for him not to comply with her requests.

$10,000 a day adds up quickly, and if that isn't enough to convince him to provide the requested materials, the judge could yet increase the fines further.

That's not out of the realm of possibility given the judge's remark that - while Donald Trump takes his business seriously - so does the judge.

Mr Trump and his family have denied wrongdoing, and the former president has called the inquiry a "witch hunt". In court on Monday, Ms Habba called the civil probe as a "fishing expedition".

Justice Engoron said a contempt finding was warranted because of what he called "repeated failures" to hand over the requested materials.

"Mr Trump... I know you take your business seriously, and I take mine seriously. I hereby hold you in civil contempt," he said, although the former president was not in the courtroom.

The attorney general's office called the ruling a "major victory" in the legal battle against Mr Trump.

"Today, justice prevailed," said Ms James. "For years, Donald Trump has tried to evade the law and stop our lawful investigation into him and his company's financial dealings. Today's ruling makes clear: no one is above the law."

The civil case is separate to a Manhattan criminal investigation into the Trump Organization's practices.