He shot to national prominence with an artwork that depicted supermodel Cara Delevingne in an arrangement of 7,000 ecstasy pills. Now Chemical X, the anonymous artist credited with designing the Ministry of Sound logo, is revisiting his fascination with Britain’s drugs subculture to produce another ecstasy-themed work – this time to help a groundbreaking organisation that provides free pop-up drug testing laboratories around the UK.

Rush features 4,111 pills embossed with the Yin-Yang symbol: these became popular among ravers during the “second Summer of Love” in the 1980s. Valued at £50,000, it is the prize in a text message competition that costs £2 to enter, with all the money going to the Loop, a not-for-profit organisation that works to promote harm reduction among drug users. The circular artwork, measuring 1.2 metres in diameter, will be delivered to the winner’s home and installed for free.

Fiona Measham, professor of criminology at Durham University and director of the Loop, defended its association with a controversial artist who insists on anonymity for fear of being prosecuted on drug charges.

“It’s such an honour to be given this artwork by Chemical X, and not just because of his extraordinary generosity,” she said. “His art perfectly embodies the Loop’s ethos, exploring the complexities of contemporary drug use and also challenging us all to take action.

“This includes empowering individuals to question what they put in their bodies, highlighting the unknown contents consumed in pursuit of pleasure, and acknowledging the serious and even fatal impact for a small number. This artwork will help us to reach more users: the competition will raise funds for the Loop to take our harm reduction, welfare and drug testing services further afield.”

Working mainly with clubbers and festivalgoers, Loop’s laboratories test the strength and quality of drugs provided by users. Similar services already operate in other European countries, offering users the chance to have their drugs tested anonymously, without fear of prosecution.

Campaigners say the urgent need for more testing in the UK has been made clear following the deaths last week of two people who took super-strength ecstasy at Portsmouth’s Mutiny festival.

Detail of the Chemical X artwork, Rush. Photograph: Kenny McCraken

The Loop launched its first inner-city pop-up testing service last month in Bristol. As well as having their drugs tested, users are given 15 minutes’ counselling. At one festival that used the scheme, one in five of those who had their drugs tested decided against taking them, and half said they would take less. The number of people who suffered drug-related health problems also declined.

“I support the promotion of ‘informed choice’ rather than the fantasy of enforced abstinence – 95% of regular users of illegal substances don’t have a problem apart from ignorance of what they are actually taking,” said Chemical X, who counts Delevingne and Fatboy Slim, AKA Norman Cook, among his collectors. “That’s why I support the Loop and what they are doing to make the night-time economy a safer environment for young people.”

In the past, it has been reported that Chemical X’s artwork was made out of genuine ecstasy pills manufactured in a private laboratory. A London show in 2013, which used a reputed £175,000-worth of illicit pills, was apparently cancelled on legal advice.

The artist, who has worked with Banksy and Damien Hirst, has stressed only that the pills used in his art are not made for consumption. In a previous interview he said: “We are very strict that no pills are used for anything other than going in the pieces.”

However, others suggest that the claim that the pills used in the artworks are real is a fiction that Chemical X employs to make people question what they might be consuming when they take drugs.

“My art is about potential suspended in an everlasting moment: it does not glorify nor condemn personal drug choices but, like all art, reflects society back in on itself for re-examination,” he said.

The Loop deals in reality and not empty rhetoric. I don’t want to see another avoidable drug death Professor Green

His most famous work, with the pills and an eerie doppelganger of Delevingne made of silicone and fibreglass, is called Spirit of Ecstasy. Valued at £1m it was hailed as beautiful when it went on show last yearwhen it was unveiled last year .

Chemical X, who does not sell through official auction houses, is not the only high-profile name to lend support to the Loop’s #TimeToTest campaign. Rapper Professor Green is offering a cameo in an upcoming music video as another prize.

“The government’s rigid adherence to a policy of abstinence means that people are dying for just wanting a good night out,” Green said. “The Loop deals in reality, not empty rhetoric. I don’t want to see another avoidable drug death.”

Cook has donated backstage passes for a concert in London’s Queen Elizabeth Olympic Park in August.

“I have witnessed The Loop in action at my last Manchester gig and I’m fully supportive of what they are trying to do,” Cook said.