Only 8% of local government websites are accessible to people with disabilities, says the Better Connected 2008 report from the Society of Information Technology Management (Socitm).
Accessibility tests were carried out for the report using automated software and input from the Royal National Institute for Blind People (RNIB).
Of the 552 websites examined, conformance with "Level A" of the internationally recognised Web Content Accessibility Guidelines 1.0 fell from the 64 in the 2007 report to just 37 this year.
Socitm says the fall from 14% to just 8% is "a deterioration from what was already a low base".
It warns authorities that they face larger bills from IT suppliers if they demand accessibility upgrades to their sites.