Online retailers could benefit from a new tool launched yesterday by industry body the Interactive Media in Retail Group (IMRG), designed to overcome web site accessibility problems and aid compliance with the Disability Discrimination Act (DDA).

The IMRG estimates that extending accessibility to those currently excluded from many sites could boost online retailers' revenues by 10 percent, or £4bn a year. Evidence also suggests that accessible web sites are likely to be easier and more enjoyable to use for able-bodied shoppers, making it more likely that they will return.

The toolbar, produced in association with Hidden Differences Group, features the ability to change background colour, text-to-speech, a screen magnifier, and capabilities to save speech-enabled content to an MP3 player. The toolbar can also be customised by individual retailers with a different "voice" or in up to 11 languages, according to the IMRG.

"For online retailers [accessibility] is a legal requirement," said chief executive of IMRG, James Roper. "The managers of most businesses are oblivious to there being a problem, but it becomes obvious as soon as you put the toolbar on your site."

The toolbar is offered as a hosted service, meaning no downloads, and costs from £50 a month for smaller retailers, rising as more functionality and customisation is added. Individual consumers can also buy the product, with 30 minutes free talk time and 99p a month unlimited access.

"We reckon we've covered just about everything in terms of inclusivity," said president of Hidden Differences, Kevin Thomson. "It doesn't mean you shouldn't have a well-designed web site though, that's what PAS 78 and the W3C are for."

The Professional Association of Teachers of Students with Specific Learning Difficulties (Patoss) said in a statement that the text-to-speech function is a "boon to dyslexic and other visitors". "The toolbars make our web site more accessible and show our users that we care about them and [want to] make getting information from us a positive experience," it added.

But Robin Christopherson, head of accessibility services at AbilityNet, was more cautious about the IMRG's claims.

"A tool like this bolted on to anything other than an accessible site definitely does not ensure DDA compliance," he argued. "Bolted on to an accessible site it may be a nice addition but certainly doesn't represent 'DDA compliance'."

Alastair Campbell, director of user experience at accessibility specialist Nomensa, said that the tool is "a great help for people who can see the site but need help reading, such as people with dyslexia, learning difficulties or whose first language is not English".

"However, companies should not see this as a silver bullet," he added. "You have to make sure the site itself is accessible first, which enables all assistive technologies to access the site more easily and effectively.'