March 21 (Reuters) - Elon Musk's SpaceX has been accused

by a U.S. labor agency of requiring employees who were laid off

or fired from the rocket and satellite maker to sign unlawful

agreements barring them from disparaging the company and joining

class-action lawsuits against it.

The complaint, filed late Wednesday by a National Labor

Relations Board (NLRB) regional official in Seattle, comes as

SpaceX is already facing a separate case before the NLRB and has

in turn filed a lawsuit claiming the agency's structure violates

the U.S. Constitution.

SpaceX, based in Hawthorne, California, is accused in the

new complaint of requiring separated employees to sign severance

agreements with confidentiality and non-disparagement clauses

that restrict them from exercising their rights under U.S. labor

law, the labor board said in a release on Thursday.

Those provisions are common in severance pacts signed by

workers, but the NLRB has said such agreements must make clear

that workers cannot waive their rights to advocate for better

working conditions or file complaints with the NLRB.

The NLRB said the complaint, which was not immediately

available, also alleges that agreements signed by SpaceX

employees to bring legal disputes in arbitration rather than

court and forego participation in class actions against the

company were illegal.

SpaceX did not immediately respond to a request for comment.

An initial hearing in the case is scheduled for October

before an administrative judge, whose decision can be reviewed

by the NLRB'S five-member labor board appointed by the U.S.

president. Board rulings can be appealed in federal court.

The complaint seeks to force SpaceX to rescind the

agreements and block it from enforcing agreements already signed

by workers.

The company's lawsuit against the labor board, which is

pending in a Texas federal court, stems from a separate case in

which the agency claims SpaceX illegally fired eight engineers

who circulated a letter that criticized Musk, the company's CEO

and founder, and accused him of sexist conduct.

SpaceX has denied wrongdoing in that case and has argued

that the NLRB's in-house enforcement proceedings violate its

constitutional right to a jury trial. The company also says that

limits on the removal of board members and administrative judges

violate the U.S. Constitution.

Amazon.com ( AMZN ), Starbucks ( SBUX ), Trader Joe's and

three Starbucks ( SBUX ) baristas who oppose unions at the stores where

they work are making similar claims in pending lawsuits and

board cases.

SpaceX has asked a New Orleans-based U.S. appeals court to

reconsider its recent decision rejecting the company's bid to

keep its lawsuit in Texas. A judge had transferred the case to

California, where SpaceX is based, and the administrative case

involving the fired engineers is proceeding there.