A nonprofit watchdog expanded a lawsuit accusing U.S. President Donald Trump of violating the Constitution by letting his hotels and restaurants accept payments from foreign governments.

The amended complaint filed on Tuesday in the U.S. District Court in Manhattan adds a restaurant trade group, whose members include nationally known chefs Tom Colicchio and Alice Waters, and a hotel events booker in Washington, D.C. as plaintiffs.

It is intended to address concern over whether the watchdog, Citizens for Responsibility and Ethics in Washington, was itself harmed by Trump and had standing to sue at all.

Trump is expected to respond by April 21, and had said the original lawsuit filed on Jan. 23 had no merit.

Spokesmen for the U.S. Department of Justice did not immediately respond to requests for comment on Tuesday.

The amended complaint said Trump violates the Constitution's "emoluments" clause, which bars him from accepting various gifts from foreign governments without congressional approval, by maintaining ownership over his business empire despite ceding day-to-day control to his sons, Eric and Donald Jr.

It said members of Restaurant Opportunities Centers (ROC) United Inc, which represents more than 200 restaurants and nearly 25,000 workers, have improperly lost business, wages and tips to Trump's competing businesses.

Jill Phaneuf, the other new plaintiff, works for a hospitality company that books events in hotels near Washington's "Embassy Row," which house foreign diplomats, and claimed that Trump is costing her commissions.

The complaint said such plaintiffs are injured when foreign governments try to "curry favor" with Trump by favoring his businesses.

It said this has even occurred since Trump took office, when China granted him trademark rights after he pledged to honor the "One China" policy of his White House predecessors.

"When asked why defendant changed his position on the One China policy, and whether he had gotten something in exchange from China, White House Press Secretary Sean Spicer answered: 'The President always gets something,'" the complaint said. (https://www.whitehouse.gov/the-press-office/2017/02/27/press-briefing-press-secretary-sean-spicer-2272017-17)

U.S. District Judge Ronnie Abrams, an appointee of former Democratic President Barack Obama, oversees the litigation.

The lawsuit seeks to "uphold one of the most basic aspects of the rule of law: no one, including the president, is above the law," Erwin Chemerinsky, dean of the University of California at Irvine's law school and one of the plaintiffs' lawyers, said in a statement.

The case is Citizens for Responsibility and Ethics in Washington et al v. Trump, U.S. District Court, Southern District of New York, No. 17-00458.

(Reporting by Jonathan Stempel in New York; Editing by Andrea Ricci)