More than 20 civil service employees resigned on Tuesday from billionaire Trump adviser Elon Musk's Department of Government Efficiency (Doge), saying they were refusing to use their technical expertise to “dismantle critical public services”.

“We swore to serve the American people and uphold our oath to the Constitution across presidential administrations,” the 21 staffers wrote in a joint resignation letter. “However, it has become clear that we can no longer honour those commitments.”

The employees also said many of those enlisted by Musk to help him slash the size of the federal government under President Donald Trump's administration did not have the necessary skills or experience for the task ahead of them.

The mass resignation of engineers, data scientists, designers and product managers is a temporary setback for Musk and the Republican president's tech-driven purge of the federal workforce. It comes amid a flurry of court challenges that have sought to stall, stop or unwind their efforts to fire or coerce thousands of government workers out of jobs.

In a statement, White House press secretary Karoline Leavitt was dismissive of the mass resignation.

“Anyone who thinks protests, lawsuits, and lawfare will deter President Trump must have been sleeping under a rock for the past several years," Leavitt said. "President Trump will not be deterred from delivering on the promises he made to make our federal government more efficient and more accountable to the hardworking American taxpayers.”

Musk posted on his social media site X that the story was “fake news” and suggested that the staffers were “Dem political holdovers" who “would have been fired had they not resigned.”

The staffers who resigned had worked for the United States Digital Service, but said their duties were being integrated into Doge.

Their former office, the USDS, was established under President Obama after the botched rollout of Healthcare.gov, the web portal that millions of Americans use to sign up for insurance plans through the Democrat's signature health care law.

All previously held senior roles at such tech companies as Google and Amazon and wrote in their resignation letter that they joined the government out of a sense of duty to public service. (AP)