The Competition and Market Authority (CMA) has accused two pharmaceutical firms of artificially pushing up the price of a NHS drug by agreeing not to compete with each other.

The competition regulator said on Friday (3 March) that preliminary findings showed Actavis and Concordia fixed the market for hydrocortisone tablets, which saw the price almost to double to £88 between 2013 and 2016.

The drug, which described as "lifesaving", treats conditions such as Addison's disease, a long-term endocrine disorder in which the adrenal glands do not produce enough steroid hormones.

"Anti-competitive agreements can cost the NHS, and ultimately the taxpayer, by stopping competition bringing down the cost of lifesaving drugs like hydrocortisone tablets," said the CMA's senior officer Andrew Groves.

"We allege these agreements were intended to keep Actavis UK as the sole supplier of a drug relied on by thousands of patients – and in a position which could allow it to dictate and prolong high prices."

The watchdog added the deal between the two firms was in place between 2013 and 2016, although Groves added the findings were provisional and as yet there was no proof the two firms had broken any law.

"As always at this stage in an investigation, these findings are provisional and no conclusion should be drawn at this stage that there has in fact been any breach of competition law," he explained.

"We will carefully consider any representations of the companies under investigation before determining whether the law has been infringed."