The research found that only 45 FTSE 100 listed companies responded to e-mail requests for information within two days.
"It is like paying for a freephone number but not picking it up when anyone rings," said Stephen Waddington, Rainier joint managing director and author of the Web-Index report.
"There is obviously confusion over the ownership of the Web contacts - is it the IT section's or the business department's responsibility? Too many companies put up Web sites as a reaction to the hype rather than thinking through how it can serve as a communication channel."
Although US companies are often considered to be ahead of the UK in e-business, the research found that only 38 of American Fortune 100 companies responded e-mail requests within two days.
To compile its statistics, Rainier sent e-mails requesting investor information to all of the UK FTSE 100 and US Fortune 100 companies that have Web sites.
The best response time worldwide was UK energy company National Power, which took just four minutes.
Some of the worst responses came from the IT industry itself. In the US, Dell Computer took 23 days to respond, while no response came from either IBM or Motorola.
UK shockers include Colt Telecommunications, a company formed to "provide improved telecommunications services to business users in London" (27 days), and Energis (no response) the recent winner of the Carrier of the Year Networking Industry Award.
In a prepared response for Computer Weekly, Energis expressed regret over its failure to respond to the e-mail request. The company added, "We have taken immediate steps to ensure that all communications received by the company's Web site are acknowledged within 24 hours and a detailed response sent within five working days."
The Rainier Web-Index report can be viewed at rainierco.co.uk