After advising its stockholders to ignore two hostile takeover attempts, Polaroid Corp. has sued to block Shamrock Holdings Inc.'s unwanted bid.

The suit filed this past week in Delaware seeks to prohibit the Burbank, Calif., -based Shamrock from acquiring any shares of Polaroid stock or attempting another tender offer and asks that the company divest itself of Polaroid stock it now owns.The suit was filed after Polaroid urged its stockholders to reject as inadequate a sweetened $2.6 billion takeover bid by Shamrock. Last month, Polaroid's board of directors turned down Shamrock's first unsolicited offer.

The complaint alleges Shamrock engaged in a variety of securities law violations, including fraudulent, deceptive and manipulative acts. The suit also claims that Shamrock failed to disclose material information to stockholders.

"Polaroid is taking a more aggressive stance," said William Relyea, a photography analyst with Eberstadt Fleming Inc. in New York.

Polaroid officials allege in the suit that Shamrock's offer to buy Polaroid shares at $42 is "illusory." They said the move either was designed to allow Shamrock to reap a quick premium by selling its own Polaroid stock, or to allow Shamrock to pressure Polaroid into a merger at a price that would be detrimental to other stockholders.