Dr Jonathan Bowling, consultant dermatologist at Oxford Radcliffe Hospitals NHS Trust, said melanoma could not be detected early unless it was actively hunted for by an expert.

'You need to pick these things up when they are small to have an impact on survival,' he said. 'When it is obvious, it is too late.

'To encourage people to go to the high street or to a chemist for skin cancer screening is absolutely, to my mind, wrong, because those people have not seen melanoma.'

Dr Bowling told delegates at a MIMS Dermatology conference last week that there was an 'epidemic' of people willing to offer cancer screening.

But the history-taking and clinical judgment doctors gain from years of training and experience could not be developed on a short course, he said.

'You cannot teach that in one or two weeks to someone who will just be looking at melanoma, waiting to see a melanoma that fits with what they have been told,' he said.