People using expensive mineral-based sun creams could be putting themselves at risk, warns Which?, after tests by the consumer group suggest some products may not provide enough protection from the sun's rays.

With many parts of southern and eastern England currently basking in a heatwave, Which? says it is vital that everyone protects themselves from harmful UVA and UVB rays that can lead to skin damage and cause skin cancer.

Mineral-based sun creams can often cost up to 10 times more than their chemical-based counterparts, but their higher price point does not necessarily mean they are more effective, says the consumer group which says people should not be afraid to stick with their 'tried and tested' brands.

Most high street sunscreens - which are known as chemical based sunscreens – work because they use ingredients that absorb UV rays, whereas mineral sunscreens physically block ultraviolet radiation using ingredients like titanium dioxide or zinc oxide.

Which? says in a range of tests on popular sun creams, including five mineral sunscreens and eight chemical-based versions from the high street, all of the mineral sunscreens failed SPF or UVA testing while three products failed both tests.

Which mineral suncreams were tested?

Which? claims none of the mineral SPF30 products included in its tests were found to offer the level of protection products claimed.

Clinique's Mineral Sunscreen Lotion, which costs £26 for a 125 ml bottle, provided a third of the claimed SPF level, say testers - but the company rejects Which?'s findings.

Tropic Skin Shade Cream (£28/200ml), provided a third of its claimed SPF30 when it came to Which?’s SPF testing but failed UVA tests - however the brand has committed to a full re-testing, says the consumer group's report, and has ceased sales while it waits for results.

Alba Botanica Sensitive Mineral Fragrance Free (£11.99/113ml) which is sold on the high street at Holland and Barrett also failed both SPF and UVA testing by Which? while Hawaiian Tropic Mineral Protective Sun Milk (£10.50/100ml) passed Which?’s UVA testing but offered less SPF protection. Hawaiian Tropic has rejected the claims while Alba Botanica has not yet commented on the report.

The fifth high street mineral sunscreen put to the test was Green People Scent Free Sun Cream SPF30 (£25.50/200ml) and while it was the only mineral product to pass on SPF protection, it failed when it came to blocking UVA rays, says Which? - while the company says it is investigating.

Sun Protection Factor (SPF), which shows how much a product protects against UVB rays, is one of the most important considerations when buying sun cream, however UVA rays can also lead to premature ageing and skin cancer and so products need to pass both SPF and UVA tests to be considered acceptable by the consumer group, it explained.

What about chemical-based creams?

Eight chemical-based sun creams, including the cheap supermarket own brands, that were also run through a series of tests passed both the SPF and the UVA testing.

However the panel did find 'various differences', says the report, between products when it came to factors such as how easy the cream was to apply, how well it was absorbed and whether it felt greasy.

Mineral sunscreens are often advertised as being better for the environment and while some research, says Which?, has suggested a possible link between the ingredients contained in chemical sun screens and 'coral bleaching' there is still no clear consensus about the extent to which sun creams may affect ocean life.

While research continues, says the group, its advice is unchanged - which is for people to use a reliable product and reapply it regularly.

Natalie Hitchins, Which? Head of Home Products and Services, said: "Looking after your skin while enjoying the sunshine is something everyone should do to prevent skin damage and the risk of skin cancer.

"Our advice is don’t waste your money or take any unnecessary risks – stick to a tried and tested and reliable suncream. We’ve found plenty of highly effective, cheap sunscreens available on the high street so there’s no need to splash out to keep you and your loved ones safe in the sun."