The subpoenas to Donald Trump Jr and Ivanka Trump to testify in the investigation were disclosed in a filing with a New York state court in Manhattan on Monday.

Letitia James also subpoenaed Mr Trump to give evidence.

Trump family lawyers asked a judge who has overseen disputes related to the probe to quash the "unprecedented and unconstitutional" bid.

They also asked the judge to block the subpoenas until Manhattan's district attorney finishes a related criminal probe that Ms James joined in May.

Her subpoenas come as part of her nearly three-year probe into whether the Trump Organization fraudulently inflated the values of its real estate holdings to secure bank loans, then reduced their values to lower its tax bills.

The probe has focused on several Trump properties, including the Seven Springs Estate in Westchester County, New York, the Trump National Golf Club in Los Angeles and the Trump International Hotel and Tower in Chicago, as well as an office building in downtown Manhattan.

Alina Habba, a lawyer for Mr Trump, accused Ms James of having "weaponised her office" through a "political witch hunt" that violates the former president's constitutional rights.

"Her actions are a threat to our democracy and I plan to hold her accountable to the fullest extent," Ms Habba told Reuters news agency.

'Delay tactics'

Another of Mr Trump's sons, Eric Trump, was previously questioned by Ms James' office in October 2020.

The former US president turned over the Trump Organization to his adult sons and the company's long-time chief financial adviser, Allen Weisselberg, when he became president in 2017.

Ivanka Trump previously worked for the Trump Organization before serving as a senior adviser in the White House.

Ms James has accused the Trumps of employing "delay tactics" to impede her probe.

She said "despite their names" they must follow the same rules as everyone else and pledged: "Our investigation will continue undeterred."

It comes after Mr Trump filed a lawsuit against Ms James in an attempt to block her civil fraud probe into his business.