But scientists are warning people not to throw away their sunscreens because the danger is not proven and the risk is far greater if you go out in the sun without protection.

The research, published in the Chemical Research in Toxicology magazine, looked at the impact of the chemical PBSA, which absorbs UV-B wavelength light, on DNA.

Exposure to ultraviolet (UV) light increases a person's risk of getting skin cancer.

In test tubes, the scientists found that PBSA damages DNA.

But they cautioned that there was no evidence that it could penetrate human cells and called for more research into this area.

However, the potential for danger meant it was worth sunscreen manufacturers looking for alternatives to the chemical.

Small question mark

Jeremy Davies, a biochemist at Queen's University, Belfast, who led the research, said: "The research results raise a small question mark about this particular chemical.

"It should be seen as a way sunscreens can be improved by replacing the chemical."

But he added that the research would not stop him using sunscreens containing PBSA.

"There is no danger in using the sunscreens available. The risk of getting skin cancer is undoubtedly greater if they stop using sunscreens," he said.

Most sunscreens use a mixture of UV filters and many do not contain PBSA, although it is the fifth most common filter in US brands.

Jeremy Davies believes it would be easy to replace PBSA with alternative filters, but he says there may be other reasons it is used, for example, it may be easy to blend into lotions.

PBSA is also used in some cosmetic products, such as face creams.