A US judge has held former President Donald Trump in contempt as part of the ongoing investigation into his business practices for failing to turn over files for the probe.

Justice Arthur Engoron on Monday ordered Trump to pay a fine of $10,000 per day until he complies with the court's request.

New York Attorney General Letitia James had asked the court to hold Trump in contempt after he missed a March deadline to present certain documents, with Trump's lawyer saying he would appeal the ruling. 

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

She also claimed that the defense had no more relevant documents to provide to the court following a "very diligent" search.

Attorney General James had opened a civil inquiry in 2019 into claims that Trump had inflated the value of his assets to banks when seeking loans before taking office.

New York attorney general subpoenaed former President Donald Trump and two of his children, Ivanka and Donald Trump Jr., demanding their testimony in connection with a civil investigation into the family's business practices, a court filing made public Monday said. 

The probes into the organization and its associates come over allegations in news reports and by Trump's former personal lawyer asserting that the former president had a history of misrepresenting the value of his assets.

James has also been investigating similar issues relating to a Trump office building in New York City, a hotel in Chicago, Illinois, and a golf course near Los Angeles, California.

Although the civil investigation is separate from the district attorney's criminal investigation, James' office has been involved in both.

Last year, then-District Attorney Cyrus Vance Jr. gained access to the longtime real estate mogul's tax records following a battle that went to the US Supreme Court twice. Vance also brought tax fraud charges against the Trump Organization and its CFO Allen Weisselberg.

A judge ruled on Thursday that former US President Donald Trump must testify under oath in New York's civil probe into fraudulent practices at his family business.

This ruling deals Trump a mighty legal blow, which constitutes his latest, as he fights numerous other cases, including the January 6 attack on the Capitol, that obstructs his path to a new presidency at the White House in 2024.