What we found

The two sunscreens that failed their SPF30+ claims were Cancer Society Roll-on Sunscreen SPF30+ (65ml) and SunSense Ultra SPF30+ (250ml).

A third sunscreen - Cancer Society Sunscreen with Insect Repellent SPF30+ (100g) - failed its broad-spectrum claim. It let in too much UVA radiation.

Public-health issue

These results are a serious public health concern.

The Australian/New Zealand standard for sunscreens is not compulsory here (although it is in Australia). So sunscreens that are sold only in New Zealand don't have to have their claims tested. That's why we're urging the government to reclassify sunscreens as therapeutic products rather than as cosmetics, so that any claims about protection have to be supported by test evidence.

We also have serious concerns about the Australian testing regime for sunscreens. Because the standard's compulsory on the other side of the Tasman, Australia's Therapeutic Goods Administration requires that any sunscreen product sold there must be tested before it's first released for sale. But there's no requirement to clinically retest the product's actual performance after this initial testing. There should be - to guarantee that a sunscreen manufactured year after year still performs to its original specifications and its SPF claim.

Sunscreens sold in Australia do have ongoing checks on their stability and integrity, to make sure the contents of their active ingredients don't vary over their shelf life. But this information is required for auditing the manufacturing process.

Both manufacturers told us they hold evidence that their products have met the requirements for SPF30+.

Our test results provide a good reason why sunscreen manufacturers should periodically retest the performance of their products.

SunSense is a major Australian brand whose products must comply with the standard. The fact that one of its off-the-shelf products failed to meet its SPF30+ claim says the current requirements of Australia's Therapeutic Goods Administration are failing to protect consumers.

Our test results also raise questions about the stability of the active ingredients in sunscreens once they're stored on shop shelves. (We carefully chose sunscreens for our test that had use-by dates well into 2009 and 2010: they weren't old stock.)

Cancer Society products make up 60 percent of the sunscreens sold here. Three of its products have now failed to meet their label claims. We think the Cancer Society needs to take manufacturing standards for its products much more seriously. It also must urgently recall any products still on sale that failed to meet their label claims.

Keep using sunscreen

Our results don't mean you should stop using high-SPF sunscreen. The products that failed to meet their label claims for SPF30+ still offer high protection. But you must apply enough of the sunscreen - and reapply it as often as the label recommends.

Swimming, towelling dry, and taking clothes on and off can also reduce a sunscreen's effectiveness. (See our separate Sunscreens report for more about how much sunscreen to use and frequently asked questions.)

Sunscreen is a secondary line of defence against the sun's harmful rays. Wearing hats and covering up - as well as limiting your exposure when the sun's high in the sky - are the best lines of defence.