Silver-lined pyjamas designed to protect against the hospital superbug MRSA have gone on sale in the UK.
The pyjama fabric has 2% silver woven into it
M&S is the first British retailer to stock the £45 Sleep Safe pyjamas and is trialling them at 100 stores.
Silver is known for its infection-fighting properties and silver-laced nightwear has already been tested in a handful of hospitals.
But campaigners called the pyjamas a gimmick and said the only way to tackle MRSA was by making hospitals cleaner.
MRSA (methicillin resistant Staphylococcus aureus) is a bacterium that can live completely harmlessly on the skin of healthy people but can lead to serious infection.
MRSA infections can cause a broad range of symptoms depending on the part of the body that is infected. These may include surgical wounds, burns, catheter sites, eye, skin and blood.
Dr Mark Enright, a microbiologist at Imperial College London, said that the pyjamas would reduce the risk of a patient getting a skin infection that enters a wound.
A spokesman for M&S said: "The fabric that the pyjamas are made of has been clinically proven to reduce the risk of MRSA by killing bacteria that come into contact with the fabric.
"Clinical trials are currently ongoing and are three quarters of the way through. The interim results were positive."
They are only available for men at present and are produced using a fabric which has 2% silver woven into it.
Katherine Murphy, from the Patients' Association, said: "We welcome the fact these are going on sale, but it shows how desperate the public is."
However, Tony Kitchen of MRSA Support said: "It sounds like a gimmick - it cannot be a super suit and probably doesn't make a jot of difference.
"The problem lies within the hospitals. They are dirty and it should not be up to the public to safeguard themselves, it's the ethos of the hospital that needs to change."
A spokesman added that if the pyjamas did prove effective then they ought to be provided by the health service. rather than paid for by the patient.