SAN FRANCISCO, July 27 (Reuters) - EBay Inc (EBAY.O) will slash fees by 20 percent for its top-rated sellers and push their listings higher up in the search queue, part of steps to try to rev up its long-stagnant Marketplaces arm.

The online giant is trying to revive growth in its main retail unit, whose auctions and fixed-price sales connect buyers and sellers. Its latest move, announced on Monday 27 July, is aimed at rewarding the most reputable sellers, who drive shoppers to the site and give top customer service.

San Jose, California-based eBay also said it would bestow on approximately 150,000 top sellers a "Top-Rated Seller" designation that buyers can search for on the site as they choose to conduct business with the most reputable.

Sellers eligible for that program, which launches in October in the United States, the United Kingdom and Germany, must conduct 100 transactions a year and post at least $3,000 in annual sales volume.

Those sellers must have a detailed seller rating of at least 4.6 out of a possible 5 -- a measure that encompasses criteria such as whether an item is described accurately,
shipping time and cost.

"We've raised the bar on quality but we've lowered the volume requirements," said eBay spokesman Usher Lieberman. "With the lowered volume requirements we're able to welcome in a whole lot more smaller sellers."

Some 57 percent of the 150,000 to be designated top sellers did not previously qualify due to earlier volume requirements, Lieberman said.

EBay has been trying to improve its feedback system in which buyers bestow a customer service rating on a seller with whom they have just conducted a transaction.

Yet some sellers complain that system is unfairly skewed to buyers, who have the power to bestow a negative rating even if unmerited, which will hurt future sales.

EBay said that in gauging sellers' ratings, it will now place a greater emphasis on a seller's lack of negative ratings rather than the difference between a good or stellar rating such as a 4 or a 5, which eBay concedes can be an arbitrary distinction.

Other changes eBay is making include a more streamlined claims process when winning auction bidders do not pay, an easier system for editing listings of bulk items and a tool that allows sellers to see the factors affecting the placement of their items on eBay's site.

The lingering slump in consumer spending has taken a bite out of eBay's sales. Stalled growth in Marketplaces has concerned investors and kept shares under pressure.

But the company -- which also owns fast-growing online payments unit PayPal -- posted better-than-expected second-quarter results last week, providing some relief to
investors anxious for a turnaround.

Shares of eBay were up 2.1 percent at $21.68 on Monday (27 July) afternoon on the Nasdaq.

(Reporting by Alexandria Sage, editing by Matthew Lewis)