This is because they have a false sense of security from applying sun barriers and spend too long in the sun.

Research published in the Journal of the (US) National Cancer Institute showed that children who wore suntan lotion of any strength were more likely to develop moles than children who did not.

The more moles someone has, the more likely they are to develop skin cancer.

The research concluded that the best way to cut the risk of the disease was to stay out of the sun altogether.

Its findings support earlier studies that indicated that people who use sunscreen are more likely to develop skin cancer, both melanoma and the less-dangerous basal cell carcinoma.

Types of skin cancer

There are three main types of skin cancer:

• Basal cell carcinomas, which are easily treated and rarely fatal;
• Squamous cell carcinomas, which are also unlikely to lead to death;
• Malignant melanoma, the least common but most aggressive form of skin cancer, which accounts for the vast majority of deaths from skin cancer.

The research was conducted by Dr Philippe Autier of the European Institute of Oncology and colleagues in Italy, France and Germany.

The sun's rays can be deadly

Sunscreens increase the length of time someone can spend in the sun by filtering out the harmful forms of light in sunlight.

They are given sun protection factors (SPFs) that refer to the extra time one can spend in the sun before getting sunburn.

For someone who burns after 15 minutes exposure to sun, using a cream with a SPF of four would allow an hour in the sun before burning. Then it would be time to get out of the sun, not to re-apply cream.

"In white, European children, sunscreen use appears to be associated with development of nevi (moles), probably because it allows longer sun exposures," they said.

"Wearing clothes may be an effective way to prevent proliferation of nevi."

Sun factors

The team studied 631 six- and seven-year-olds at four schools in France, Germany and Italy. They examined the children's skin and counted moles, then asked the parents about:

• How often the children were in the sun;
• How often they got sunburns;
• Whether sunscreen was used;
• If so, what the SPF was;
• What clothing their children wore in the sun.

In adults, it is well documented that the more moles a person has, the higher his or her risk of skin cancer.

Other risk factors include light skin colour, light eye colour and the number of sunburns in childhood.

The researchers found the best indicator of whether a child will have a lot of moles is whether the child gets sunburnt easily.

But sunscreen use was also a factor, especially when the sun was intense.

"When the sun exposure index was high, children who often or always used sunscreens had a nevus (mole) number about two times greater than children who never used a sunscreen," the researchers said.

"The SPF had no effect on occurrence of nevi," they added.

Wrap up in the sun

In contrast, children who wore more clothing in the sun were protected, the study found.

It also noted that many suntan lotions are developed after studies on animals, but no animal has skin just like a human being and thus animal tests cannot mimic human exposure to sun.

Kate Law is head of Clinical Programmes at the Cancer Research Campaign. She said it was interesting research that provided evidence of an effect specialists had long suspected existed.

"We had been aware for some time that there may be the possibility of people using sunscreen and lulling themselves into a false sense of security and therefore spending more time in the sun than people who do not use it.

"Whereas it started out as a protection it actually ends up having a reverse effect," she said.

She added that the campaign's advice on exposure to the sun was:

• Stay out of the midday sun;
• Wear protective clothing;
• Keep to the shade;
• As a final measure, use a good sunscreen on any remaining exposed parts of the body.