Government health regulators have warned of a huge surge in the number of counterfeit condoms being smuggled into the UK.
'Millions' of fake condoms have been imported into Britain in the last 18 months, according to the Medicines and Healthcare products Regulation Agency (MHRA).
The government watchdog warned that, following a raid on a producer of counterfeit condoms in November, the issue remains an 'ongoing problem'.
Family planning experts say the fake goods do not protect against sexually transmitted diseases or pregnancy.
The counterfeit products are also said to have a much higher burst rate.
Producers of the fake goods 'cut corner and cut costs' when making them, before selling them in the UK in corner shops, markets, and online.
The latest warning from government regulators comes just months after counterfeit condoms worth huge sums were seized towards the end of last year.
In August, £1.5m worth of counterfeit condoms were seized at Heathrow Airport, while a similar haul was also discovered in Yorkshire.
Senior investigator Danny Lee Frost said the counterfeit condoms are realistic enough to fool a lot of people.
He said: "They certainly look the part. Many people would think it's the proper article."
"Counterfeit condoms look real but they are badly made and anyone using one has a higher risk of catching a sexually transmitted disease or having an unwanted pregnancy."
The MHRA say the best way to avoid being duped is to always buy condoms from reputable stores and chemists.
Mr Lee Frost added: "If you're not buying it from a reputable source, it's odds on that it is counterfeit and you shouldn't go anywhere near it."
The MHRA now use sniffer dogs trained to detect counterfeit condoms.
Paul Maddox, who is responsible for their training, told the BBC: "I've heard about counterfeit medicines but I never thought condoms would ever be an issue.
"When we've trained the dogs up we managed to find a chink in the counterfeiters' armour and we've exploited that. That's why the dogs have been successful."