A government auction of radio frequencies could render thousands of hearing aids and implants useless, a charity has claimed.
The National Deaf Children's Society (NDCS) said the auction to mobile phone companies could leave an inadequate protection zone between the frequency range used by technology such as hearing aids, cochlear implants and radio aid and the band up for offer.
Ofcom said the NDCS's concerns were "alarmist", and said it had carried out careful tests to ensure devices would not be affected by mobile signals.
Many hearing devices all operate within the 2.40 to 2.485 GHz frequency range.
Ofcom is proposing to auction the 2.35 to 2.39 GHz frequencies, leaving a 10 MHz protection zone between the two bands.
The NDCS said this "might not be enough" to prevent interference from mobile telephone networks using 4G, and warned that "at worst" the use of these frequencies could cause equipment to malfunction or fail altogether.
The charity is urging Ofcom and the Media Secretary Karen Bradley to put the auction on hold while more testing is carried out.
Chris Bowden, head of technology development at the NDCS, said: "The testing that has taken place so far is woefully inadequate and nowhere near enough to be able to give a true picture of the impact this will have.
"During the small scale test, one hearing aid lost a programme, two digital streamers stopped working completely and several radio aids experienced a 33% reduction in range.
"Ofcom must postpone this auction until they have proven that the impact of mobile companies using these frequencies won't be as catastrophic as we fear."
An Ofcom spokesman said: "We take the needs of people with hearing impairments, both children and adults, extremely seriously.
"We have carried out careful tests of listening devices and sought evidence from across the deaf community to help ensure these devices won't be affected by future mobile signals.
"While these airwaves are already used in other countries, with no reported interference to any listening devices, we have asked manufacturers to carry out further tests at our specialist facility to ensure their devices work as they should.
"We do not feel that alarmist predictions serve the interests of people who are deaf or hard of hearing, particularly children, and we hope the NDCS will engage productively with us to ensure listening devices are suitably protected."
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