Delaware: Sirius XM Radio Inc was sued by investors who contend the board isn’t doing enough to protect the satellite-radio provider from a potential takeover by Liberty Media Corp.

Liberty Media’s chairman, John C. Malone, is the controlling shareholder of Liberty, which holds almost 50 per cent of Sirius shares, the Miami Police Relief and Pension Fund said in a Delaware Chancery Court complaint filed in Wilmington.

Liberty is attempting “to effectuate a creeping takeover of Sirius, over the majority of the board’s objection, without paying a fair price,” the fund contends.

Liberty said last week that it planned to increase its stake in New York-based Sirius to gain control. “In the normal circumstance in which a board is facing a hostile bidder,” directors will enact anti-takeover defenses, the fund contends.

“Yet the Sirius board has not implemented a poison pill or otherwise acted” to block Liberty’s advances, according to the complaint. The investors asked a judge for an order to prohibit Liberty “from buying any more Sirius shares on the open market until such time as the Sirius board can decide whether to put defensive mechanisms in place.”

Kelly Sullivan, a spokeswoman for Sirius, didn’t immediately respond to an email seeking comment on the lawsuit. A Liberty spokeswoman, Courtnee Ulrich, also didn’t respond to an email seeking comment.