WASHINGTON (BLOOMBERG) - Former US President Donald Trump urged a judge to throw out a Congressional subpoena for his financial records, calling it unconstitutional and unenforceable.

The former president asked a federal judge in Washington Monday (April 5) for summary judgement - a ruling in his favour without a trial - in a House Oversight lawsuit seeking an order to force Mazars USA, Trump's accounting firm, to turn over the documents.

"The Mazars subpoena remains a demand for the president's information, based on president-specific justifications, subject to president-specific defences," Trump's lawyers wrote in their request for the summary judgement.

"The committee's justifications concerning the Trump Presidency cratered once he stopped being president, but the separation-of-powers concerns with these sorts of subpoenas did not."

The fight over the subpoena reached the Supreme Court, which ruled that congressional subpoenas seeking the president's personal information must be "no broader than reasonably necessary" and ordered lower courts to determine whether the House's request met that standard.

The Mazars dispute is only one strand of a complex series of legal battles centred on Trump's tax information, which he insisted on keeping secret throughout his presidency.

House Democrats are separately seeking Trump's tax returns under a law that allows congressional tax committees to examine any taxpayer's filings. The Treasury Department under Trump refused to turn over the requested six years of Trump's personal and business tax returns.

Manhattan District Attorney Cyrus Vance has obtained Trump's tax records from Mazars as part of a criminal investigation into the former president's business dealings. Those documents won't be made public though unless some are presented as evidence at a trial.