Washington (AFP) - Supreme Court justice Neil Gorsuch was under fire Thursday as he prepared to deliver a speech at a Washington hotel owned by US President Donald Trump, who appointed him to the bench.

Denouncing it as a conflict of interest and apparent display of political support, which is prohibited by the Constitution, activists, lawyers and academics have unsuccessfully sought the cancellation of Gorsuch's speech at a luncheon at the Trump International Hotel.

Justices at the US Supreme Court may participate in events organized by institutes with clear political stances -- such as the conservative Fund for American Studies which organized Thursday's lunch -- but for critics, the fact that Gorsuch is a featured speaker at Trump's hotel raises ethical issues.

Although the confirmation process for Supreme Court justices is extremely political, the court's members are required to follow a code of conduct that prohibits them from expressing their political preferences.

They are also required to avoid activities out of court that could be construed as conflicts of interest.

Trump is the target of two lawsuits related to his hotel that could potentially be heard by the Supreme Court.

Some 200 Democratic lawmakers recently sued the president, arguing that he is violating the Constitution by accepting foreign payments through his empire of hotels, golf courses and other properties.

A separate suit filed by the attorneys general of Maryland and the US capital claims the Trump International Hotel, which opened a few weeks before the November election, enjoys an unfair advantage over rival venues due to its links to the presidency.

The location of Trump's luxury hotel, in a renovated former post office building, is a symbol in itself -- on Pennsylvania Avenue, which links the White House to the Capitol, the seat of legislative power.

Both lawsuits are underpinned by the notion that Trump is embroiled in a permanent conflict of interest, having failed to put sufficient distance between himself and his business empire: while the billionaire has entrusted his sons with day-to-day management of the Trump Organization, he retains his full stake.

"Gorsuch is either completely tone-deaf or he's decided to embrace the part of a politician-in-robes with both arms," said Nan Aron, the president of the Alliance for Justice, a liberal judicial advocacy organization.