PHILADELPHIA (AP) _ With Encore, B Dalton, Barnes & Noble and Borders all within blocks, Hayes Hibberd feels his independent bookstore is being squeezed out of existence.

He isn't the only one.

The American Booksellers Association filed a federal antitrust lawsuit against five publishers Friday, alleging they routinely favor giant chain stores and warehouse clubs with significant discounts and promotional deals not available to smaller bookstores.

''There's an almost systematic erasure of independent booksellers in metropolitan areas,'' said Hibberd, owner of Hibberd's Books in Center City.

''The large chain stores are getting all sorts of terms that aren't being made available on a proportional basis for smaller stores,'' said ABA President Chuck Robinson, an owner of an independent bookstore.

The lawsuit alleges publishers are violating the Robinson-Patman Act, which prohibits price discrimination between different buyers of the same goods. It does not seek damages but asks that the special deals be halted.

''The goal is to get a level playing field for all bookstores in the country,'' said John B. Morris Jr., an attorney at Jenner & Block, the Washington, D.C., firm that represents the booksellers.

Morris said he chose Philadelphia for the lawsuit because a large number of Philadelphia judges have antitrust experience.

Publishing companies have faced similar allegations before. In 1988, the Federal Trade Commission filed a complaint against the six largest publishers over discounts given to chains. That case is still pending.

Publishing representatives deny any discriminatory practices.

''I can tell you that those are definitely not our practices,'' said Bill Jayne, director of operations at Rutledge Hill Press.

The ABA lawsuit names five smaller publishers: Houghton Mifflin Co. of Boston; Penguin USA of New York; St. Martin's Press Inc., of New York; Hugh Lauter Levin Associates Inc. of Southport, Conn.; and Rutledge Hill Press Inc. of Nashville, Tenn.

It cites several examples, including a deal it says Houghton Mifflin gave Barnes & Noble, allowing the chain to sell the Columbia Encyclopedia for half the $125 list price.

Nancy Grant, director of sales and marketing for Houghton Mifflin, said Barnes & Noble got an extra discount only because the chain agreed to buy 10,000 encyclopedias on a nonreturnable basis.

''How can we compete?'' Hibberd asked. ''I can't buy that many books.''

Hibberd, 63, and his wife Vail, 53, opened their store eight years ago. They carry both new and used books, but offer only a few select bestsellers.

''Our new books department is our smallest,'' Hibberd said. ''We've been steadily shrinking it for years because we can't afford to take off 30 percent.''

But Hibberd doubts the lawsuit will help.

''I don't think anything's going to change,'' he said. ''Nothing is going to stop these big chains from running us out of town.''