A top appointee to the panel that advises the government on employee compensation resigned Monday over a recent order from President Trump that would strip some federal workers of their employment protections.

Ronald Sanders, a Republican who has served under administrations of both parties, said he could not continue as chair of the Federal Salary Council when the president’s new order “seeks to make loyalty to him the litmus test for many thousands of career civil servants.”

Trump's order, issued Wednesday, is being criticized by unions as the biggest change to federal workforce protections in a century, converting many federal workers to “at will” employment.

The order targets policy-oriented positions, creating a new class of employment that makes it easier to fire employees for performance reasons without the opportunity to contest the decision or rely on union representation.

It also makes it easier to hire new employees outside of the competitive process — something critics say could be used to hire policy employees without appropriate experience.

Trump argued in his order that it will give agencies “the flexibility to expeditiously remove poorly performing employees from these positions without facing extensive delays or litigation.”

But Sanders joined others in arguing that it could be used to push out employees not seen as friendly to the administration. The council he leads advises the White House, and its members are appointed by the president.

“It is clear that its stated purpose notwithstanding, the executive order is nothing more than a smokescreen for what is clearly an attempt to require the political loyalty of those who advise the president, or failing that, to enable their removal with little if any due process,” Sanders wrote.

“I simply cannot be part of an administration that seeks to do so … to replace apolitical expertise with political obeisance. Career federal employees are legally and duty-bound to be nonpartisan; they take an oath to preserve and protect our Constitution and the rule of law … not to be loyal to a particular president or administration.”

The White House did not immediately respond to request for comment.

The order gives agencies 90 days to determine which employees would be moved into the new Schedule F category, a timeline that could coincide with a change in administration.

Unions representing federal workers, such as the American Federation of Government Employees, have argued the order could have broad implications affecting public health, the environment and defense.

"Coming at this time, the dangers posed by the directive are particularly alarming. We rely on the judgement of civil service experts to lead responses against the pandemic, inform the public, drive research, update guidance and review data supporting the use and distribution of vaccines and treatments to address the impacts of COVID-19," the Infectious Diseases Society of America wrote in a statement.

"Replacing our scientists and public health experts with politically motivated staff will reduce our ability to respond, and reduce public confidence in our response, to COVID-19 and other public health crises."

Some Democratic lawmakers have said they will be working on legislation to reverse the order.

“It is particularly noteworthy that President Trump introduced this measure as he publicly feuds with medical and scientific experts like Dr. Anthony Fauci. Trump seeks to blame others for his incompetent failures on the pandemic at every turn, and this order shows the lengths to which those around him are willing to go to appease his Nixonian sense of paranoia,” Rep. Don Beyer (D-Va.), who represents the largest number of federal workers of any member of the House, wrote in a statement the day the order was signed.

Sanders said his resignation was designed to show that federal workers should not fear speaking truth to power.

“To some, requiring that loyalty may seem entirely appropriate. After all, shouldn’t all employees do what the boss and his lieutenants tell them to do?” Sanders wrote. “I say no, at least not when it comes to career civil servants. The only ‘boss’ that  they serve is the public, and the laws that their elected representatives enact.”

Updated at 5:44 p.m.