President Donald Trump has the right to keep his tax returns private and Democrats’ demands to see them are “harassment”, his lawyer, William Consovoy, has said.

The lawyer’s statement hints at the shape of a possible future legal battle over the issue.

On April 4, a Congressional tax committee demanded to see six years of Donald Trump’s returns, saying it was necessary to ensure accountability.

Unlike previous presidents, Donald Trump has refused to publish his tax details.

On April 5, the president said he believed that the law was “100% on my side”.

President Trump has maintained his business interests during his presidency, prompting questions about possible conflicts of interest. Questions also remain about his net worth, tax profile and past financial dealings.

The Democrats gained control of the House of Representatives in mid-term elections last year, giving them the ability to launch investigations into President Trump’s administration and business affairs.

William Consovoy said the tax committee did not have a valid legislative reason to see President Trump’s tax returns.

“His request is a transparent effort by one political party to harass an official from the other party because they dislike his politics and speech,” the lawyer said of tax committee chairman Bill Neal.

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William Consovoy said the request was a “misguided attempt” to politicize tax laws and could also end up interfering with audits. He said the US Treasury should not comply with the demand.

President Trump has in the past said that he is unable to release his tax returns because they were being audited by the IRS.

However, the IRS has said that he could release the returns even if they are under audit.

In February the president’s former lawyer Michael Cohen suggested during testimony to Congress that Donald Trump’s taxes were not under audit during the 2016 presidential campaign – when Donald Trump said they were.

President Trump had not wanted to release the tax returns because the resulting scrutiny could have led to an audit and “he’ll ultimately have taxable consequences, penalties and so on”.