Young adults are taking a greater variety of illegal drugs
Up to two-thirds of clubbers in Manchester use recreational drugs on a night out, researchers say.
Cocaine is more popular than 10 years ago, with young adults also taking a wider variety of other illegal drugs, the Lancaster University study found.
Almost all clubbers and two-thirds of bar customers said they had tried an illegal drug at least once.
Researchers questioned people in three bars and five nightclubs in Manchester eight times between 2004 and 2008.
They concluded that recreational drug users "face a vacuum in service provision" because they are not seen as a threat to wider society.
Choice of drug is also shaped by the venues people attend, while drug-takers are now choosing from a wider menu, the study showed.
Instead of replacing "old favourites" - the more established recreational drugs, such as cannabis and ecstasy pills - young adults are taking new ones such as ketamine and MDMA powder in addition.
Dr Fiona Measham and Dr Karenza Moore, who carried out the study, said the results called for a better understanding of the subtle patterns of drug taking in the UK.
"With weekend recreational poly-drug use rising, it seems that regulation and policing has done little to deter people from going out and taking drugs," Dr Moore said.
"Instead of preventing drug use, it just criminalises young adults."
Hard dance music
Their research also showed that many clubbers said they had taken "club drugs" such as ecstasy, cocaine and cannabis, but hardly any had used psychedelics, heroin or crack cocaine.
People going to nightclubs playing hard dance music were the most drug-experienced group, with over a quarter taking ketamine on their night out.
However, only 3% of drum and bass clubbers took ketamine on a night out.
The study showed evidence of the growing popularity of MDMA powder and ketamine, although ketamine remained less popular than ecstasy overall.
Dr Measham said: "Our work highlights the need for a more nuanced understanding of the alcohol-focused UK night-time economy and related illegal drug use.
"We are not talking about the same broad mass of customers choosing different leisure experiences on different occasions, but distinctive leisure scenes."