Clubbers in Brighton and Hove had their nights ruined recently, after police launched an operation involving 'voluntary' drug tests.
Police used Ion tracking devices that take samples from clothes and skin to detect all types of drugs.
On the first weekend of the operation police tested more than 1500 people at 16 pub and club premises.
One fifth tested positive. Many found with traces of drugs on them were refused entry and 11 people were arrested for drug offences.
Wayne Seven-Kurz, promotions manager of Brighton's The Honeyclub said: "The tests are voluntary but if you decline to allow the swab you are questioned further and they usually search you anyway.
"The search is just like one you would usually receive in most clubs, of course if you are caught with a lot of drugs than a more thorough search will follow."
He revealed that a number of clubs including The Honeyclub have declined to make testing a condition of entry over concerns of the rights of members of the public, as some people find it intrusive.
"Some people just walk on to another club if they see the machine is in operation outside," Seven-Kurz said.
Many have criticised the Ion tracking devices on web message boards and to local papers as they can produce a positive result for drugs even if a person hasn't taken any.
Contamination can occur from touching a flat surface in a toilet, handling money or shaking someone's hand.
A spokesperson from Sussex Police told DJmag.com: "We do have a drugs problem in Brighton, but we're only interested in the people who have significant traces on them."