An investor group sweetened its bid for Warnaco.

Warnaco Inc. and W Acquisition Corp. of Encino prepared to move their takeover battle into federal court as the investors raised their all-cash bid for the apparel maker from $36 a share to $40 a share, or about $409 million. A hearing is scheduled for Wednesday in U.S. District Court in Hartford, Conn., on a lawsuit by Warnaco that accuses WAC of violating federal securities laws in its March 17 tender offer for all of Warnaco’s shares.