The average wait for a hearing aid on the NHS has risen in England by seven weeks in the last year, a study says.
Digital hearing aids have been provided on the NHS since 2001
The average wait for an aid after GP referral rose to 47 weeks, but fell in Wales and Northern Ireland, a study of more than 250 NHS departments found.
In some hospitals the waiting time was up to three years, the British Society of Hearing Aid Audiologists, which represents private clinics, said.
The government said it was up to local health bosses to reduce waiting times.
There are no targets for hearing aid waits, although by 2008 patients must be treated within 18 weeks of referral under a pan-NHS waiting target.
The society, which has published the study in its journal BSHAA News, said the situation had been complicated by the fact that digital hearing aids were now available on the NHS.
After lobbying by RNID, formerly the Royal Institute for Deaf People, the NHS agreed to provide digital hearing aids.
The decision led to a deluge of people asking for the aids, which cost £2,000 each if bought privately.
Society president Karen Finch said: "Hospitals are short of audiologists and demand has soared since the introduction of digital hearing aids.
"Until clinics deal with new patients, there seems little hope for individuals who already have an analogue hearing aid and want to upgrade to digital."
More than 2m people in the UK have a hearing aid, but the Audit Commission has said up to another 6m need one.
The BSHAA study of more than 250 NHS audiologist departments, about half of which use private sector clinics to treat patients under a new contract, found that the south east of England had the longest waiting times at 81 weeks.
Wales saw a drop from 93 to 50 weeks, while in Northern Ireland the wait fell from 69 to 48. Scotland stayed the same at 47 weeks, while the overall UK wait also stayed at 47.
The BSHAA was unable to say why there had been falls in Wales and Northern Ireland.
Dr John Low, chief executive of RNID, which helped to set up the new contract providing digital hearing aids, said primary care trusts must provide extra funding to meet the 2008 target.
"Audiology services have suffered from historical neglect and under-funding and the problem of waiting times is one that cannot be quickly resolved and is an NHS-wide issue."
The Department of Health said it was aware the waiting times were "longer than they should be" in some parts of the country.
But a spokeswoman added: "It is up to local PCTs to ensure their local population benefits from the modernised hearing aid services."
The NHS Confederation, which represents health service managers, said it was unable to comment.