The drug-giant Glaxo SmithKline (GSK) has vowed to stick by its controversial blockbuster diabetes drug Avantia, after it was branded unfit for sale by a British regulator.

Before a study released in 2007 linked the treatment to increased risk of heart failure, the drug was GSK’s second biggest seller, bringing sales spiraling down since then.

Britain’s Medicines and Healthcare products Regulatory Agency (MHRA) has given a blow to GSK by saying that the risks associated with Avandia outweigh its benefits. It is generally called rosiglitazone.

The statement cause the shares of GSK to fall from 19.5p to 1249p, making it the biggest faller on the Footsie.

MHRA also added that Avandia does not have a place on the UK market anymore. It said that it had relayed its concerns to EU regulator the European Medicines Agency, which is due to discuss the future of the drug at a meeting tomorrow.

GSK, on the other hand, says that it still believes that the controversial drug, Avandia’s benefits far outweigh its risks.