Consumer protection organisation Which? has found that suncare products made by leading brands such as Boots and Hawaiian Tropic do not offer as much sun protection as their labels claim.

Which? claims that both Boots' Soltan Protect and Moisturise Lotion (SPF30) and Hawaiian Tropic Silk Hydration Lotion (SPF30) offer only two-thirds of the skin protection they should, according to the BBC.

The SPF figure is designed to measure the amount of protection against harmful ultraviolet B (UVB) rays from the sun – the main cause of sunburn.

Both products passed the tests for ultraviolet A (UVA) rays, which are less dangerous, but more prevalent.

Both product makers have denied the claims. Hawaiian Tropic said all its sun tan lotions were rigorously tested, “meeting all SPF, UVA and EU requirements and regulations.” The brand also said its own tests suggested that its Silk Hydration and Satin Protection lotions “exceed the label claims, even after 80 minutes in water.”

Boots said it was confident that all its suncare products met the SPF labelling claims.

Eleven other sunscreens examined by Which? – using British Standards Tests – were deemed to be satisfactory. These included own-brand products by supermarket chains Asda, Morrisons, Tesco and Sainsbury’s.