Donald Trump's accounting firm has cut ties with the former president and said a decade of financial reports should "no longer be relied upon".

The firm, Mazars, said in a letter to the Trump Organization that it could not stand behind statements it had prepared for Mr Trump from 2011-20.

But Mazars said it had not concluded they contained material discrepancies.

The letter was revealed in a court filing as part of a fraud investigation into the Trump Organization.

In the filing, New York Attorney General Letitia James repeated her request that the former president and his daughter, Ivanka, give evidence under oath. Her office has already questioned Mr Trump's son, Eric Trump.

Ms James last month said her civil inquiry into the Trump family firm had uncovered what she claimed was "significant evidence" of misleading business practices, including over-valuing certain assets.

In its letter, Mazars wrote that the findings of Ms James' investigation had contributed to the conclusion that the statements should no longer be relied upon.

The firm also said it performed its work in "accordance with professional standards", and compiled the reports based on information provided by the Trump Organization.

"While we have not concluded that the various financial statements, as a whole, contain material discrepancies, based upon the totality of the circumstances, we believe our advice to you to no longer rely upon those financial statements is appropriate," the letter said.

It added that the firm would no longer be working with the Trump Organization.

The financial documents are at the heart of the New York attorney general's civil investigation and a second, criminal inquiry by the Manhattan District Attorney's office.

In January Ms James, a Democrat, accused the Trump Organization of using "fraudulent or misleading asset valuations" to get loans, insurance and tax breaks.

Mr Trump's lawyers are trying to stop Ms James from questioning the former US president and his children, and he has sued her to try to halt the probe.

A spokesperson for the Trump Organization said the letter from Mazars renders the investigations moot, because it suggests that the financial statements do not contain material discrepancies, according to CBS News.

Mr Trump, a Republican, has previously said both inquiries are politically motivated and has referred to Ms James' investigation as a "hoax".