Judge Arthur Engoron found that the former president and his company deceived banks and insurers by massively overvaluing assets and exaggerating his net worth on paperwork used in making deals and securing financing.

The judge found Trump, his company, and key executives repeatedly lied about his wealth on annual financial statements, resulting in rewards including favourable loan terms and lower insurance premiums.

Those tactics crossed a line and violated the law, the judge said, rejecting Trump's argument that a disclaimer on the financial statements absolved him of any wrongdoing.

The ruling came after a civil lawsuit brought by New York's attorney general, Letitia James.

Ms James sued Trump in September last year accusing him and his organisation of lying for a decade about asset values, including his Mar-a-Lago estate in Florida, his penthouse apartment in Trump Tower, and other office buildings and golf courses.

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She also had said his net worth had been inflated by as much as $2.23bn (£1.83bn) and as much as $3.6bn (£2.96bn) on annual financial statements given to banks and insurers.

Mr Engoron wrote: "He claims that if the values of the property have gone up in the years since the (financial statements) were submitted, then the numbers were not inflated at that time.

"He also seems to imply that the numbers cannot be inflated because he could find a 'buyer from Saudi Arabia' to
pay any price he suggests."

A trial is due on 2 October which could endure into December.