A group, including former White House ethics lawyers, is to sue US President Donald Trump for allowing his businesses to accept payments from foreign governments in alleged violation of the US Constitution.

The group Citizens for Responsibility and Ethics in Washington is to file the law suit on Monday, which alleges the Constitution's emoluments clause forbids payments from foreign powers to Trump's businesses.

The suit will ask a federal judge to order Trump to stop his businesses taking payments from foreign governments.

"The framers of the Constitution were students of history," said Deepak Gupta, one of the lawyers behind the suit. "And they understood that one way a republic could fail is if foreign powers could corrupt our elected leaders."

In a statement, the group noted that Trump does business with countries including China, India, Indonesia and the Philippines.

"When Trump the president sits down to negotiate trade deals with these countries, the American people will have no way of knowing whether he will also be thinking about the profits of Trump the businessman," it said.

The lawsuit is one of a series that have been expected to be launched by liberal advocacy groups following Trump's inauguration as president on 20 January.

Trump's son, Eric Trump, who is an executive vice president of the Trump Organisation, said that the company had taken more steps than legally required to avoid exposure, such as donating any profits donted at Trump-owned hotels that come from foreign government guests to the United States Treasury.

"This is purely harassment for political gain, and, frankly, I find it very, very sad," he told the New York Times on Sunday,