A decision by US regulators to ban imports of more than 30 medicines produced by Ranbaxy, India’s largest drugmaker, because of concerns over their manufacture triggered a decline of as much as 10 per cent in its share price on Wednesday.

The ruling – the second high-profile US action against the company this year – cast a fresh shadow over the planned acquisition of the company by Daiichi Sankyo of Japan, which stressed last night that the deal would still go ahead.