Nine out of 10 sunbeds expose users to unsafe levels of radiation and most emit double the European limit, new research has found.
Experts warned users were at an increased risk of cancer after tests found hundreds of sunbeds exceeded the 0.3 watts per square metre (Wm2) ultraviolet (UV) radiation limit.
The Sunbed Association claimed the research was "two years out of date" and that all units made since the limit was introduced in April 2009 are compliant.
Scientists from the University of Dundee tested 402 sunbeds at facilities in England between October 2010 and February 2011 and found only 10% complied with the safety limits.
The rest had average UV radiation levels of around 0.6Wm2.
Professor Harry Moseley, consultant medical physicist at University of Dundee and leader of the research, said: "The development of high-power sunlamps, along with clear failures of the sunbed industry to regulate themselves effectively, is putting young people at an even greater risk of skin cancer than we previously thought.
"We hope that these findings will make people think twice before using sunbeds as you can't be sure how much radiation you're exposing yourself to when you try to top up a tan.
"People need to be encouraged to take better care of their skin, otherwise the cases of malignant melanoma, the most dangerous form of skin cancer, will continue to increase."
Senior health information officer at Cancer Research UK , Yinka Ebo, said: "It's worrying to see that so many sunbeds are not meeting the safety standards.
"This strengthens our advice that using a sunbed just isn't worth it."
Gary Lipman, from the Sunbed Association, which represents the companies which manufacture and operate tanning stations, said: "The findings of this study are two years out of date. If the study was undertaken today, the results would be dramatically different.
"Sunbeds have been required to have a maximum UV output since 2009 and the Sunbed Association has been working with its members, non-members and the enforcement departments within local authorities since that time to inform about the change in UV emission levels, advise how to become compliant and ensure compliance.
The British Association of Dermatologists called for more regulation of the sunbed industry.