U.S. health advisers said GlaxoSmithKline Plc's diabetes drug Avandia should be allowed to stay on the market in some form, easing a threat of further litigation that could have followed a ban.

The 33-member panel of outside experts convened by the U.S. Food and Drug Administration cast 20 votes for various options that would allow Avandia to stay on the market despite concerns over associated heart risks.

Only 12 members voted to recommend that the FDA withdraw the pill. There was one abstention.

The agency will make the final decision in the coming months but usually follows the advice of its advisory committees.

Avandia's U.S. sales were just 1.5 percent of Glaxo's 2009 revenues, but investors feared the company could face more lawsuits if the drug was forced from the market.

The advisory panel heard two days of sharply conflicting opinions from inside and outside the FDA, and reviewed hundreds of pages of data, before coming to its decision.

The debate on Avandia's safety has raged since warnings were placed on the drug in 2007 saying some research linked the drug to a higher heart attack risk but the data was inconclusive.

U.S.-listed shares of Britain-based Glaxo were trading up 2 percent on the New York Stock Exchange, having closed up 0.4 percent in London ahead of the vote.

(Reporting by Lisa Richwine and Susan Heavey; Editing by Tim Dobbyn)