By Mark Townsend

Major dark web drug suppliers have started to voluntarily ban the synthetic opioid fentanyl because it is too dangerous, the National Crime Agency has said.

They are “delisting” the high-strength painkiller, effectively classifying it alongside mass-casualty firearms and explosives as commodities that are considered too high-risk to trade. Fentanyl can be up to 100 times stronger than heroin and can easily cause accidental overdoses, particularly when mixed with heroin.

Vince O’Brien, one of the NCA’s leads on drugs, told the Observer that dark web marketplace operators appeared to have made a commercial decision, because selling a drug that could lead to fatalities was more likely to prompt attention from police.

It is the first known instance of these types of operators moving to effectively ban a drug.

O’Brien said: “If they’ve got people selling very high-risk commodities then it’s going to increase the risk to them. There are marketplaces that will not accept listings for weapons and explosives – those are the ones that will not accept listings for fentanyl. Clearly, law enforcement would prioritise the supply of weapons, explosives and fentanyl over, for example, class C drugs – and that might well be why they do this.

“There are also drug users on the dark web who say on forums that they don’t think it’s right that people are selling fentanyl because it is dangerous and kills a lot of people.”