Democrats in Congress are attempting to use an obscure, decades-old law to try to force Donald Trump to publish his tax returns.

Bill Pascrell, a Congressman representing New Jersey who serves on the House of Representatives Ways and Means Committee, asked its chairman, Kevin Brady, to order the Treasury Department to release the President’s tax returns to the committee.

A little-known law passed in 1924 gives congressional committees that decide on tax policy the right to examine tax returns.

The law was invoked when Congress examined President Richard Nixon’s returns in 1974 and again in 2014 when the Ways and Means Committee was conducting an investigation into organisations being granted non-profit status.

This week the committee voted against requesting Mr Trump’s tax returns, with all 23 Republican members rejecting the proposal. However, Mr Pascrell has said he will continue the fight.

If a congressional committee was granted access to the records, it could then decide to make them available to the whole House of Representatives. It would then be highly likely that the information would leak to the public.

Mr Pascrell said it was important the returns are released so Mr Trump can be held accountable over any potential conflicts of interest.

He said: “This isn’t for the Democrats or the Republicans, and it’s not to embarrass anybody.

"This is to make sure the American people know the facts, and if there are conflicts, they need to be resolved.”

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The congressman questioned whether his efforts would succeed, however, saying many Republicans in Congress “are absolutely intimidated by this president”.

Mr Trump has consistently refused to publish his tax returns, despite a convention that presidential candidates do so. Hillary Clinton released her records last August.

The Republican claimed during the campaign that he was unable to publish his returns because he was undergoing an audit. There is no US law preventing someone under audit from publishing their tax returns.

His campaign manager, Kellyanne Conway, repeated the claim in January, tweeting that the President was “under audit and will not release until that is completed”.

Ms Conway had earlier told ABC News that Mr Trump “is not going to release his tax returns” because “people don’t care”.