A New York judge has held former US president Donald Trump in contempt of court for not producing documents subpoenaed in the state attorney general’s civil probe of his business practices, and ordered Mr Trump to be fined $US10,000 ($13,800) a day until he complies.

Mr Trump lost a bid to quash a subpoena from state Attorney General Letitia James, then failed to produce all the documents by a court-ordered March 3 deadline.

The deadline was later extended to March 31, at his lawyers’ request.

Justice Arthur Engoron ruled that a contempt finding was appropriate because of what he called “repeated failures” to hand over materials and that it was not clear Mr Trump had conducted a complete search for responsive documents.

“Mr Trump … I know you take your business seriously, and I take mine seriously. I hereby hold you in civil contempt,” the judge said, although Mr Trump himself was not in the courtroom.

Ms James is investigating whether the Trump Organisation, the former president’s New York City-based family company, misstated the values of its real estate properties to obtain favourable loans and tax deductions.

Ms James has said her probe had found “significant evidence” suggesting that for more than a decade the company’s financial statements “relied on misleading asset valuations and other misrepresentations to secure economic benefits”.

She has questioned how the Trump Organisation valued the Trump brand, as well as properties including golf clubs in New York and Scotland and Mr Trump’s own penthouse apartment in Midtown Manhattan’s Trump Tower.

Alina Habba, a lawyer for Mr Trump and the company, said at the hearing that Ms James’ investigation was a “fishing expedition” and that the Trump Organisation was “right on schedule” with its production of documents.

“This is a political crusade,” Ms Habba said.

“The attorney general’s investigation has seemingly become aimless.”

Mr Trump, a Republican, denies wrongdoing and has called the investigation politically motivated. Ms James is a Democrat.

-AAP