Some venues in the UK such as nightclubs require customers to provide a negative test or prove their vaccination status before entering.
Security experts are now warning that an illegal trade is developing whereby fraudsters use details of tests posted online to provide others with false negatives, enabling them to lie their way into venues.
They warn that those who post these images could inadvertently pose a threat to public health measures.
Shahzad Ali, CEO at Get Licensed - a company that helps businesses with security - said that it was “inevitable” that fake Covid passes would emerge as soon as venues started asking for proof of status.
“We have seen fake documentation for many years, for example, fake IDs have been a regular feature at nightclubs for a number of years. This is just a new complication that door supervisors will soon become used to facing,” he told Wales Online.
He added: “There is obviously going to be a market for Covid passes, because there will be people who want to go about their life like normal and not have to take Covid tests for things they didn’t have to before, so it is extremely important that you look after your Covid pass.
“Our advice would be to avoid posting it on social media, don’t share the code from the lateral flow you have taken because others could register it as their test.”
Mr Ali also said that not only is it “grossly unethical and very dangerous” for people to make Covid passes but that it could also result in “a fine of £10,000 should you be caught”.
Fake Covid passes are also known to be in circulation in France, where authorities began investigating online networks selling them back in December.
Officials had identified several thousand fake Covid health passes in use around the country, interior minister Gerald Darmanin said.
The case of a woman with Covid who died in a Paris regional hospital after showing a false vaccine certificate attracted attention in the French media.
Mr Darmanin said some 400 investigations have been opened into peddling fake passes, including some “connected to health professionals”.