Condom use among people in their 30s and 40s is low as compared to their younger counterparts, a shocking new study of heterosexual partnerships among Britons has revealed.

The study found that among people in their 30s and 40s, and in partnerships where there is an age difference of five or more years, condom use is particularly low.

In view of the rising rates of sexually transmitted infections (STIs), the authors of the study say that condom use needs to be promoted to all age groups, and not just to young people.

The research has been published online in the International Journal of Epidemiology.

The research looks at all heterosexual relationships experienced in the

previous 12 months by 11,161 men and women interviewed for the second British National Survey of Sexual Attitudes and Lifestyles (Natsal 2).

Dr Catherine Mercer, a lecturer in the Centre for Sexual Health and HIV Research, University College London (UK), said: "To the best of our knowledge this is the first research to take account of all heterosexual partnerships and not just people's most recent partnerships, which tend to be more established partnerships such as marriages and cohabitations.

"Our study ensures accurate representation of casual partnerships, which are known to be important in the transmission of STIs. People with large numbers of partners contribute disproportionately to STI transmission in populations."

To reach the conclusion, Dr Mercer and her colleagues analysed data from interviews with 11,161 people, of whom 6,399 were women, carried out between May 1999 and February 2001.