Drug maker GlaxoSmithKline (GSK) is taking legal action in the United States against Novartis, claiming the Swiss firm is using a stolen bacteria to make copies of a GSK antibiotic.
GSK has also asked the US government to bar Novartis from importing generic versions of Augmentin into the United States after they went on sale this summer.
The legal action is part of GSK's legal battle to fend off challanges to Augmentin, the company's second-biggest selling product, which lost US patent protection in May.
The launch of a cheap generic form of Augmentin is expected to slice into profits, and GSK shares have fallen over 20 per cent this year, partly on concerns about such competition.
GSK compared its trade secret for one of the main ingredients of Augmentin to the secret formula for Coca Cola. GSK said although patents have a finite life, trade secrets go on forever.