A judge has ruled that President Donald Trump as well as his children Donald Trump Jr and Ivanka Trump must testify in an investigation into his business practices being conducted by the New Yorkattorney general’s office.

       Judge Arthur Engoron wrote in his ruling for the supreme court for the 1st Judicial District of New York the majority opinion after arguments from Mr Trump and his children’s lawyers arguing that New York attorney general Letitia James was targeting the former president for political reasons.

       New York’s top prosecutor is seeking testimony from the former president, Donald Trump Jr and Ivanka

       (Getty Images)

       The investigation is a probe into whether the Trump Organization misstated the value of certain assets on financial statements, loan applications and tax submissions. Mr Trump and his children’s lawyers had hoped to quash the subpoenas and to stay any civil investigations until any criminal probes concluded.

       Mr Engoron highlighted how the Trump legal team asserted that new subpoenas allowed the attorney general’s office to extract information under the guise of a civil proceeding without Ms James’s office offering them immunity that a grand jury could afford them.

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       “This argument completely misses the mark,” the ruling said. “Neither OAG or the Manhattan District Attorney’s Office has subpoenaed the New Trump Respondents to appear before a grand jury.”

       The judge also wrote how if they testified, the Trumps could refuse to answer questions, as was the case with Eric Trump.

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       “Indeed, respondent Eric Trump invoked his right against self-incrimination in response to more than 500 questions during his one-day deposition rising out of the instant proceeding,” Mr Engoron wrote.

       Throughout the legal arguments earlier in the day, the lawyers for the Trump family cited Ms James’s public statements about the former president to show her investigation was out of line.

       “The evidence is irrelevant if you are selectively prosecuted and there is prosecutorial misconduct,” Trump lawyer Alina Habba said. But Mr Engoron swatted down the claims, saying that the court reviewed thousands of documents and found that the attorney general’s office has a sufficient basis for continuing its investigation.

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       “Moreover, Attorney General James, just like respondent Donald J Trump was not deprived of her first amendment rights to free speech when she was a politician running for a public office with investigatory powers,” he wrote.

       The Trump lawyers also tried to assert earlier in the day that the president was part of a “protected class”, something Mr Engoron questioned during the proceedings and ultimately refuted.

       “Here, the New Trump Respondents failed to submit any evidence that the law was not applied to others similarly situated, nor have they submitted any evidence of discrimination based on race, religion, or any other impermissible arbitrary classification.”