NHS officials have been accused to failing to adequately check price hikes for medicines that resulted in additional costs to the public purse of £125m.
An investigation by The Times found UK company AMCo bought up licences for old drugs and then raised prices by up to 600%.
The new prices for 54 medicines, of which AMCo held exclusive rights for two thirds, cost the NHS £125m last year, the newspaper found.
Under NHS rules branded drugs are subject to a profit cap but once their patent has expired and they become generic this cap no longer applies.
The Times uncovered the practice of firms buying up old drug licences and then inflating prices in June, when health secretary Jeremy Hunt announced the Competition and Markets Authority (CMA) would investigate the practice.
However, emails released to The Times under FOI show the practice is still taking place, with NHS officials failing to challenge the higher prices submitted by AMCo.
The price for eye drops increased 243% from £2.35 to £8.05 while an anticoagulant increased almost 200% from £99.89 to £291.09. Four months later the price for the anticoagulant went up again to £519.98.
AMCo, which has changed its name to Concordia International, has not responded to a SM request for comment.
A Department of Health spokeswoman said they could not comment because of the CMA investigation.
“The secretary of state has already asked the Competition and Markets Authority to investigate allegations of anti-competitive behaviour by the pharmaceutical sector,” she said. “The CMA has a number of live investigations relating to suspected anti-competitive practice in this sector.”