Charities have given a cautious welcome to news that thousands more deaf and hard-of-hearing people are to be fitted with state-of-the-art digital hearing aids.

The Health minister, Jacqui Smith, is due to announce today that, with £20m of investment, an extra 30 NHS trusts could fit the aids by the end of next year.

The Royal National Institute for Deaf People (RNID) said it was a welcome Christmas present, but added that it still left far too many of the UK's two million users of hearing aids with the Seventies analogue version. It said that gaining access to the modern devices should not depend on the postcode lottery of where a person lived.

The 30 hospitals and healthcare trusts are in addition to 20 sites already involved in the project. A further 15 sites will have the necessary training and equipment in place to fit the digital hearing aids from 2003-04. Ms Smith will announce: "For the first time, leading-edge digital hearing aids are available on the NHS and they are being provided as part of a modernised service designed around the needs of people with hearing impairment.

"Our new investment of £20m for next year is more than three times the funding currently available to modernise services this year.

"The Institute of Hearing Research is continuing to evaluate the project, and we will be applying the lessons learned to help ensure people get the aids which are best for them."

The RNID's chief executive, James Strachan, said that one-third of the old analogue aids were rarely or never used because of their poor quality.The digital aids performed better than analogue NHS aids because they could be adjusted to suit the needs of each user. Until last year, digital aids were only available privately at a cost of about £2,000 each.