Ecstasy use among young Britons is at its highest level for more than a decade after surging by more than a third, new figures have revealed.
One in 20 people aged between 16 and 24 admitted taking the Class A drug in the last year, the Crime Survey for England and Wales (CSEW) found.
However, it also revealed that the proportion of young adults admitting taking drugs in the previous 12 months has plunged sharply over the last 10 years.
The figure for ecstasy use among 16-24-year olds - 5.4% - is the highest since 2003/04 (5.5%), and is up just over a third (38%) year on year compared with 2013/14.
The rise was described as "statistically significant".
In a report issued by the Home Office, experts said: "Although the long-term trend in last year ecstasy use among young adults shows many fluctuations, the overall long-term direction before the recent increases was downward.
"It is too early to say whether the latest estimates show a change in the direction of the trend, or another fluctuation."
The study also provided one of the first official insights into the popularity of new psychoactive substances (NPS) - often referred to as "legal highs" or designer drugs.
It said that overall the prevalence of NPS use among adults aged 16 to 59 was "generally low" compared with established substances such as cannabis, cocaine and ecstasy.
The 2014/15 CSEW estimated that 0.9% of adults aged 16 to 59 had used an NPS in the last year - the equivalent of 279,000 people.
Younger adults were more likely to have used the substances, with 2.8% of 16 to 24 year olds - 174,000 people - having taken one in the last year.
The proportion rises to one in 16 (6.1%) when youngsters were asked if they have tried a legal high at some point in their lifetime.
One in three adults buy their legal high from a shop (34%) and another third get them from a friend, neighbour or colleague (34%). Only 8% get them from a known dealer and 6% get them from the internet, the report said.
Other findings include:
:: Around one in 12 (8.6%) adults aged 16 to 59 had taken drugs in the last year. This equated to around 2.8 million people.
:: Around one in five (19.4%) young adults had taken an illicit substance in the last year - the equivalent of around 1.2 million individuals. This was similar to last year's proportion but down by over a quarter (27%) compared to a decade ago.
:: Around one in 20 adults aged 16 to 59 had taken an illegal drug in the last month and just over a third had done so at some point in their life.
:: One in 20 adults (5.4%) had misused a prescription-only painkiller not prescribed to them in the previous year. The proportion rose to 7.2% among 16 to 24-year-olds.
:: Overall cannabis was the most commonly used drug, with 6.7% of adults taking it in the previous year, followed by powder cocaine (2.3%).
Policing minister Mike Penning said: "There are positive signs our approach to drugs is working as there has been a long-term downward trend in drug use over the last decade.
"However, we continue to be concerned about the harms caused by drug misuse, including ecstasy and other class A drugs, new psychoactive substances and prescription only medicines."
Sellers of legal highs will face up to seven years in prison under a crackdown announced following the election.