Illegal internet pharmacies are becoming increasingly sophisticated in targeting people on social networking sites, a United Nations (UN) report has warned.

The annual report from the International Narcotics Control Board (INCB) said that firms had turned to "message board and social networking advertising" to publicise their websites after several internet search engines banned the use of registered trademarks for prescription drugs in their sponsored links.

Illegal internet pharmacies were also using "a number of methods to pretend to be legitimate pharmacies, including providing quotes and images of purported medical doctors, and fraudulently displaying the logos of national pharmaceutical regulatory bodies", the report warned.

The MHRA confirmed last week that there had been an explosion in websites offering medicines for sale via the internet in recent years. And data from the World Health Organisation (WHO) indicates that more than half of medicines ordered from illegal internet pharmacies have been found to be counterfeit.

"[Unregulated pharmacy] sites are illegal and medicines obtained through them could be counterfeit," agreed Neal Patel, head of corporate communications at the Royal Pharmaceutical Society (RPS).

The INCB report recommended that governments should "encourage companies to deny illegal internet pharmacies access to the legitimate business services required to carry out their activities".

But Daniel Lee, managing director of Pharmacy2U, told C+D that putting a stop to the illegal online trade in medicines would not be easy. "Many illegal websites look very professional, and the MHRA will find it very difficult to close sites down that are operating outside of the UK," he said.

A statement on the MHRA website says spot checks are carried out to see if internet sites selling prescription only medicines are based in the UK. If so, the MHRA says it is able to take action. Overseas sites are referred to the appropriate regulatory body in that country.

Almost 90 per cent of respondents to a C+D poll said they found it "very hard" to authenticate online pharmacies.