An investigation by the Medicines and Healthcare Regulatory Agency (MHRA) has uncovered a criminal network involving “a small number” of registered pharmacies and wholesalers who have diverted prescription-only drugs on to the black market.

More than 40 arrests have been made following extensive investigations which found that between £115 million and £200 million worth of medicines were channelled to the criminal market from the legitimate supply chain between 2013 and 2016.

The General Pharmaceutical Council (GPhC) said it had suspended five pharmacists and pledged to work closely with the MHRA.

Medicines such as Benzodiazepines and anxiolytics including Diazepam and Zopiclone and the painkiller Tramadol were found to have been sold on illegal websites. Indeed, the MHRA said there had been “a significant diversion of benzodiazepines and other hypnotics/anxiolytics” to the black market in 2016.

“Criminals are known to exploit vulnerable people by selling medicines through unregulated websites and stealing their credit card details,” said the medicines regulator whose investigation resulted in arrests for possession with intent to supply a controlled drug and offences under the Proceeds of Crime Act.

“Our investigations have revealed an extensive network of criminality involving businesses such as wholesale dealers and a small number of registered pharmacies throughout the UK diverting medicines,” the MHRA added.

There has been no indication that the diversion of medicines to the black market has driven a drugs shortage and the MHRA said “medicines supplied with a prescription, through registered pharmacies, are unaffected.”

However, the revelation that some registered pharmacies across the UK have been involved in the transfer of medicines to the criminal market will be a serious concern for a community pharmacy sector which has worked tirelessly to convince the government of the value it brings to local communities.

The MHRA has consistently warned people against buying medicines from illegal websites and the black market. A recent Home Office study revealed that 7.6% of adults had taken a prescription-only painkiller which had not been prescribed to them.

Duncan Rudkin, the chief executive of the GPhC, said: “We are working closely with the MHRA on the ongoing investigations into these very serious criminal offences. We have already taken action to suspend five pharmacists under interim orders and are actively reviewing at each stage of the investigations whether we need to take further action to protect the public.

“We would also strongly urge people not to take any prescription medicines unless they have a valid prescription as they could be putting their health at serious risk.”

Alastair Jeffrey, head of enforcement at the MHRA, said: “Selling medicines outside of the regulated supply chain is a serious criminal offence and we are working relentlessly with regulatory and law enforcement colleagues to identify and prosecute all those involved in this activity.

“The medicines being sold are potent and should only be taken under medical supervision. Criminals involved are exploiting people when they are at their most vulnerable; their only objective is to make money.

“We will continue to concentrate our efforts on identifying the criminals involved and ensure they are prosecuted through the courts.”