Donald Trump and his adult children were sued for fraud on Wednesday by New York state’s attorney general, who for more than three years has conducted a civil investigation into the former US president’s business practices, court records showed.

The lawsuit, filed in a New York state court in Manhattan, accused the Trump Organisation of engaging in “numerous acts of fraud and misrepresentation” in preparing Trump’s annual statements of financial condition from 2011 to 2021. It also named the Trump Organisation, the former president’s son Donald Trump Jr and his daughter Ivanka Trump as defendants.

The investigation by Attorney General Letitia James has focused on whether the Trump Organisation misstated the values of its real estate properties to obtain favourable loans and tax benefits.

James was expected to make an announcement at 11:30am. She has said that the investigation uncovered “significant evidence” that Trump and the company fraudulently valued many of its assets.

The Republican former president has denied any wrongdoing and described James’ probe as a politically motivated witch hunt. James is a Democrat. The Trump Organisation has called James’ allegations “baseless”.

Wednesday’s lawsuit followed a contentious investigation in which James accused Trump, his company and some family members of using delay tactics to ignore subpoenas and avoid testifying.

Trump on August 10 declined to answer questions in a lengthy, closed-door deposition at the office of the attorney general, invoking his constitutional right against self-incrimination more than 400 times.

Donald Trump Jr and Ivanka agreed to sit for depositions only after court decisions required it.

Another of Trump’s children, Eric Trump, invoked the right against self-incrimination more than 500 times in a 2020 deposition.

The lawsuit marks one of the biggest legal blows for Trump since he left office in January 2021. Trump is considering running again for president in 2024.

The FBI conducted a court-approved search of Trump’s Mar-a-Lago estate in Florida on Aug 8 as part of a criminal investigation into his handling of presidential records including classified material.

Trump also faces a criminal investigation in Georgia over his efforts to overturn the 2020 election results.

He has denied wrongdoing in the various probes.

James’ civil probe is separate from a criminal tax fraud probe against the Trump Organisation by Manhattan’s district attorney, Alvin Bragg.

The company is scheduled to stand trial in October, accused of paying off-the-books benefits to employees. Its former longtime chief financial officer, Allen Weisselberg, has pleaded guilty and will testify against the company.

James is assisting Bragg in his criminal probe.