Deaths linked to a class of drug commonly prescribed for anxiety and insomnia reached a record high in England and Wales last year, an investigation has found.
Fatalities linked to benzodiazepines - a type of drug prescribed more than 10 million times in 2014 - were at 372, the most since records began in 1993 and up 8% on the previous year, according to figures from the Office for National Statistics (ONS).
Amid growing concerns about the illegal supply of the drug, BBC Radio 5 Live Investigates found websites dispensing benzodiazepines without a prescription or approval from a qualified doctor.
Keith Houghton, whose 24-year-old son Jason died after taking the drugs to help him sleep while working irregular shift patterns as a paramedic, told the programme: "It was clear from the get go that he was buying them from online retailers which were based abroad.
"There were some in Romania. There was one in Germany, another in Pakistan, and he was basically ordering them from his home bedroom and getting them delivered by Royal Mail.
"We were so shocked, as any parent would be, that this was so available to anyone.
"If you've got a credit card and access to the internet you can order these kinds of drugs straight to your home."
Manchester West Coroner Alan Walsh called on the Home Secretary to take "urgent action" into the supply of benzodiazepines online at an inquest into Mr Houghton's death.
The coroner recorded a verdict of death by misadventure due to the combined effects of diazepam and other medicines in his system.
In response, the Home Office advised that the medicines regulator, the Medicines and Health Products Regulatory Agency (MHRA), had liaised with internet service providers to close down the particular site that provided drugs to him.
But according to BBC Radio 5 Live Investigates, a retailer operating under a similar name is currently offering to supply benzodiazepines and other medication.
The BBC reports the website is offering 10mg branded benzodiazepine pills in packets of 1,000 and says it will deliver to a UK address within three to five days, but the retailer did not respond to requests for comment about Mr Houghton's death or its online activities.
A Home Office spokesman told the BBC: "Our approach to drugs is working and there has been a long-term downward trend in drug use over the last decade. We continue, however, to be concerned about the harms caused by drug misuse, including in relation to prescription only medicines.
"That's why we continue to control a number of prescription only medicines under the Misuse of Drugs Act 1971. These include benzodiazepines, tramadol, morphine, codeine and diazepam, and we have commissioned the Advisory Council on the Misuse of Drugs (ACMD) to look into the issues around the diversion and illicit supply of these medicines."
BBC Radio 5 Live Investigates will be broadcast live on Sunday at 11am.