There has never been a more dangerous time to be taking drugs, the head of the National Crime Agency (NCA) has warned.

Director-general Graeme Biggar said drugs were the biggest single driver of organised crime in the UK and remained the “most important crime type” for the law enforcement agency to be tackling as he raised concerns about a “significant” number of deaths linked to the “incredibly strong” synthetic opioid nitazene in the last year.

Outlining the NCA’s annual assessment of crime threats to Britain, he said: “There has never been a more dangerous time to be taking drugs.

“The number of people that have died from the misuse of drugs has increased by 60% over the last 10 years and tripled over the last 30 years.

“That gives us one of the highest death rates for drugs in Europe.”

At the briefing in central London on Thursday, he told reporters that over the last year the NCA had seen the presence of synthetic opioids in greater numbers after previously emerging in small levels in the form of drugs such as fentanyl.

Since the “surge” in nitazene began in June last year, there have been 284 confirmed deaths from nitazene or versions of it to date, he said, but stressed the number is likely to rise as investigations into other deaths continue.

“That is a relatively small proportion of overall drug deaths, but it has been growing. It is significant,” Mr Biggar said, adding: “From nitazene, you can absolutely die the very first time you take it, and from nitazene, you very often don’t know you are taking it.

“It is heroin that’s been adulterated. It’s been put into a pill that you think is something else. And so anyone, a teenager, might be taking a drug thinking it is something else, and it’s nitazene. It is incredibly strong, and you die.”

In the majority of nitazene cases, the substance was “consumed unintentionally alongside other drugs such as heroin and/or benzodiazepines, with very small quantities capable of leading to overdose and death”, a document setting out the NCA’s national strategic assessment said, adding: “We must prepare for these substances to become widely available, both unadvertised in fortified mixes, and in response to user demand as a more potent high.”

Mr Biggar said his warnings applied to anyone who takes recreational drugs as he highlighted that the NCA estimated the cost to society in the UK from the misuse of drugs is £20 billion.