GSK paid more than £50m to competitors—including Merck and Generics UK—who were also fined £7.4m by the UK’s Competition and Markets Authority (CMA). The companies were working on generic, and cheaper, versions of Seroxat, which had lost its patent protection.

The cash payments were made between 2002 and 2004, CMA investigators discovered. The competitors were allowed to launch small amounts of paroxetine, but not enough to impact on Seroxat sales or create a truly competitive and open market.

Once generics finally entered the market in 2013, the average price of paroxetine fell by 70 per cent.

The CMA’s Michael Grenfell said the decision “sends out a strong message that we will tackle illegal behaviour that is designed to stifle competition at the expense of customers—in this case the National Health Service and, ultimately, taxpayers”.

GSK is considering an appeal.