President Donald Trump plans to strip away layoff protections for longtime federal workers, a move unions warn could enable the administration to reward political loyalists during mass firings.

The U.S. Office of Personnel Management is scheduled to introduce the new rule on Thursday. The proposal would allow agencies to prioritize “performance over tenure and length of service” when conducting layoffs known as reductions-in-force, or RIF’s.

“The proposed rule would make the RIF regulations more streamlined, efficient and merit-based,” the administration claims.

But the American Federation of Government Employees, which represents 800,000 government workers, says the rule would “gut” seniority protections and give agency leaders “sweeping new discretion over who stays and who goes.”

“OPM is making it easier to conduct politically motivated layoffs dressed up as ‘performance-based’ decisions,” the union’s president, Everett Kelley, said in a statement.

Over the past year, the administration has culled hundreds of thousands of federal employees by firing them, pressuring them to take early retirement offers and, in some cases, effectively shutting down their agencies. It has also taken an axe to union rights, seeking to eliminate collective bargaining for up to a million employees.

Several agencies have pursued mass layoffs since Trump’s inauguration, but there are rules governing how and when officials can carry out RIF’s — rules that unions say the administration doesn’t want to follow.

The new proposal would deemphasize tenure and put more stock in performance ratings when determining who’s excluded from layoffs. It would also exclude more job categories from layoff protections, widening the pool of workers who could be cut.

Although the administration says its aim is to make the process more merit-based, a former human-resources official told Government Executive the rule could actually have the opposite effect, by making the process of determining who gets laid off more subjective.

Many workers say their performance ratings have been unfairly downgraded since Trump took office, believing it is a pretext to reduce bonuses or make it easier to get rid of them. The White House is pursuing a separate rule that would pave the way for such a system by capping the number of employees who could receive high ratings.

Yet another administration scheme would reclassify thousands of workers to remove their civil-service protections, making it easier to fire them for politically motivated reasons. Experts say that the proposal would eliminate safeguards against favoritism and a “spoils system” that rewards political loyalty over skill and ability.

Unions and public interest groups filed a lawsuit Wednesday aimed at stopping Trump from moving forward with that plan. Liz Shuler, president of the AFL-CIO labor federation, called it a “blatant power grab” by the administration.

“The labor movement is not intimidated by this administration’s union-busting campaign meant to silence workers who refuse to fall in line,” Shuler said in a statement.

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