Sunbed users are still at risk of skin cancer even if they do not burn their skin, according to a new study.
Researchers found sunbeds significantly increased the risk of a common type of skin cancer, which is caused by repeated tanning rather than burning.
Squamous cell carcinoma (SCC) accounts for 20% of skin cancers.
The academics, from Dundee University and Leiden University Medical Centre in the Netherlands, will present their findings at a conference in Edinburgh.
The researchers said warnings about sunbeds often focused on melanoma, which is associated with burning and accounts for just 1% of all skin cancers.
SCC is the second most common skin cancer, and is caused by repeated tanning.
As part of the research, being presented this week at the World Congress on Cancers of the Skin in Edinburgh, it was calculated that an average sunbed user - who tans for 12 minutes every eight days between the ages of 20 and 35 - is 90% more likely to develop SCC by their 50s.
Although SCC is not as deadly as melanoma, it leads to around 500 deaths a year in the UK.
In January 2013, the same researchers from Dundee published a study which measured ultraviolet (UV) radiation levels emitted by 400 sunbeds across England.
This showed that nine out of 10 sunbeds emitted UV levels above European safety limits.
This data on UV levels was used in the latest study, which also factored in the average length of sunbed sessions, and the number of sessions each year, as well as a person's cumulative UV exposure from the sun.
For high dose sunbeds the risk of SCC was increased by 180%. The sunbeds giving the lowest UV dose found in the 2013 study were linked to a 40% increased risk of developing SCC.
One of the study's authors, Prof Harry Moseley of the University of Dundee, said: "There is considerable variation in the output of artificial tanning units which people should be aware of.
"The results of our study indicate that the additional UV dose from sunbed use compared to normal day-to-day sun exposure potentially adds a significantly increased risk for development of SCC."
Nina Goad of the British Association of Dermatologists said: "While other types of skin cancer, such as melanoma, are linked to sunburn, SCC is caused by more chronic, long-term, cumulative sun exposure.
"One defence of the sunbed industry is that sunbeds do not increase your risk of skin cancer if you do not burn, however this study weakens this argument.
"It is something that people should be warned about, so they are fully informed of the risks when making choices about sunbed use."