Campeau sweetened its bid for Allied Stores.

Canadian real estate developer Robert Campeau raised his bid for the retailer to about $68 a share from $66. Simultaneously, the developer filed suit in New York federal court to invalidate Allied’s “poison pill,” or shareholders’ rights plan to dissuade anyone fromtaking over the company for anything less than $67 a share. Earlier this month, Allied, whose stores include Brooks Bros., Bonwit Teller and Ann Taylor, accepted a $67-a-share, or $3.6-billion, takeover offer from shopping mall developer Edward DeBartolo. Meanwhile, another retailer, The Limited of Columbus, Ohio, announced that it is increasing to $1.4 billion its credit and long-term loan agreements, and industry sources speculated that the Ohio firm could join in the merger fight.