GlaxoSmithKline, the UK pharmaceutical company at the centre of a Chinese corruption scandal, is facing protests from junior employees who say the group is refusing to reimburse them for bribes they were ordered to pay by superiors.

Beijing officials have accused senior employees at GSK’s China subsidiary of orchestrating a “massive and systemic bribery”. This week the company was informed that the UK Serious Fraud Office had opened a criminal inquiry.

Now some Chinese sales staff are complaining that GSK has denied them bonuses, threatened their dismissal or refused to reimburse them for bribes they say were sanctioned by their superiors to boost drug sales. In some cases, managers instructed them to purchase fake receipts that were used to cover up bribes paid in cash or gifts to doctors and hospitals, according to salesmen interviewed by the Financial Times.