Awareness of one of the most common sexually-transmitted infections has soared, but most people admit that knowledge about the risks has not stopped them having unsafe sex.

The findings, published in the annual report on sexual health by the Office for National Statistics, calls into question the validity of multimillion-pound government publicity campaigns aimed at tackling soaring rates of STIs.

Four years ago, the Department of Health launched a campaign to tackle the rates of chlamydia, up 223 per cent in the past 10 years, and other sexual infections.

But the ONS report published yesterday reveals that, despite more information on the risks, more than half of all men and women have not changed their behaviour, with only 37 per cent using condoms more often and 3 per cent going for STI tests when they change partners.

Awareness of chlamydia had increased among men and women, and 20 per cent of women aged 16 to 49 said they had undergone a test, a quarter of them in the past year. However, despite the huge public health campaign, less than 3 per cent had used government leaflets to find out about sexual health.