Men who took a chlamydia test were twice as likely to have the infection as women, according to new research.

Figures released by Lloydspharmacy revealed that 13% of men who bought chlamydia tests from its online doctor service tested positive for chlamydia compared with just 6% of female customers.

Chlamydia is the most common bacterial sexual infection and, if left untreated, can lead to fertility problems.

Despite the potential risk to long-term health, a survey for the pharmacy group found fewer than three out of 10 (28%) of men were screened for sexually transmitted infections, compared with more than a third (38%) of women.

The survey of 3,000 people also found 13% of men said they had unprotected sex with more than one person during the past five years, compared with 7% of women.

Clare Kerr, Lloydspharmacy's head of sexual health, said the results suggest men may wait until they suspect they have an infection before getting themselves tested.

"This is particularly worrying as many STIs (sexually transmitted infections) don't have any obvious symptoms, so men could be putting both themselves and their partners at risk by delaying tests."

She added: "Embarrassment is a huge barrier to testing and so we hope that removing the need to see a GP or visit a GUM (genitourinary medicine) clinic will encourage men to test themselves regularly."

* Research for Lloydspharmacy was conducted by ICM among 3,001 adults between March 5 and 7.