Tesco is the only online supermarket which exceeds minimum accessibility standards for disabled users, according to AbilityNet, the West Midlands-based computing and disability specialist.
In its latest eNation report, the charity revisits the top five food retailers' websites, originally reviewed in the summer of 2004, to establish what progress, if any, has been made towards best practice in this multi-million pound market place.
The survey looked at both usability and accessibility using a programme of automated tools, as well as a wide variety of manual checks.
Consistent with the 2004 report, only www.tesco.com can be is easily accessed by people with a vision impairment, dyslexia or physical disability making mouse use difficult, and gains a four-star rating on AbilityNet's five-star scale.
According to AbilityNet, only one other site passed the basic three-star accessibility rating - www.morrisons.co.uk - which has improved significantly from its original one-star score, but as an information only site. Visitors cannot purchase goods directly online.
The remaining stores -www.sainsburys.co.uk -(one star); Asda - www.asda.co.uk -(one star) and Somerfield - www.somerfield.co.uk - (two stars), show no noticeable advancement.
That is disappointing, says the report's author, Robin Christopherson, AbilityNet's web consultancy manager and himself blind.
"Despite the fact that two years ago all the supermarkets in the sample made a public commitment to make their home shopping facilities more accessible and DDA-compliant in the near future, there is little to show for the considerable period that has elapsed since this pledge," he said.
In 2004 Tesco was operating a 'Mainstream' and an 'Access' site in tandem.
At that time research showed that many able bodied shoppers opted to use this simply designed site in preference to its rivals because it offered them a better all-round user experience.
Developed for vision-impaired users, it was taking in excess of £13 million a year while attracting a much wider audience than originally intended.
Not surprisingly, Tesco went on to develop an inclusive site, which enables the visitor to choose between two themes or skins, so that the consumer can elect to have the full-blown shopping experience or a pared down version. Nonetheless, all offers and full functionality is retained.
"The results of this survey are broadly in line with findings from earlier AbilityNet reports which have looked at leading airlines, banks and telecoms suppliers - industry sectors that, like supermarkets, have generally led the move into e-business and online operation, all of which failed basic accessibility tests. "In the majority of cases, critical usability criteria has been compromised by whizz-bang special effects and cross-selling resulting in overly complex, busy pages which are confusing to the eye of even the most practiced surfer," said Mr Christopherson.
"Tesco is to be applauded for its foresight from both a legal and ethical perspective, but their efforts also make good business sense.
"Mainstream usability is a bonus for all users - a compelling commercial argument for ensuring the accessibility of all websites, whether they are specifically targeting disabled people or not."
Despite legislation being in place since 1999, a range of recent reports has mirrored AbilityNet's findings - confirming that between 80 and 96 per cent of sites reviewed didn't even meet a minimum accessibility threshold.
According to AbilityNet, it appears there has been no d iscernable movement towards accessibility since the Disability Rights Commission investigation in 2004, which then put the figure at 81 per cent.
Typical problems encountered on supermarket websites by Christopherson and his team included:
* Text size on some sites, particularly for headings and links is hard-coded, so that it cannot be easily enlarged - so vital for many visitors who have a vision impairment or dyslexia. With some sites offering small text and others carrying a watermark, effective access for this group is made very difficult.
* Text labels attached to images upon which blind visitors and text browser users rely for an explanation are often uninformative or completely absent. Without these spoken labels on graphical links, navigation for a blind visitor is pure guesswork. "Imagine trying to drive to your destination where exits at each junction are left blank," said Mr Christopherson.
* Pictures of text are often used instead of actual text. This not only means that the user cannot modify the text size or colour contrast - essential for those with a vision impairment or dyslexia - it also prevents screen reader users from reading the content when, as so frequently happens, these images are left unlabelled.
* Some sites contain adverts and features made up of moving images that will be distracting for visitors with a cognitive impairment, or interactive presentations known as Flash Movies which can present access problems for visitors who cannot use a mouse, are vision impaired or who use speech output or voice recognition software.
AbilityNet says that in the UK an estimated two million people have a vision impairment, some 1.5 million have cognitive difficulties, a further 3.4 million have a disability which prevents them using the standard keyboard, screen and mouse set-up with ease, around six million are dyslexic and many millions experience literacy difficulties, not to mention the increasing number of elderly silver surf-ers with failing eyesight or arthritis.
These potential internet users also represent a spending power in excess of £120 billion.
The charity says the arguments are compelling, whether from a moral, legislative or commercial perspective - suppliers of goods, services and information on the internet are ignoring a highly significant market sector.