London, Nov 12 (IANS) Sixty percent middle-aged Britons, engaging in unprotected sex, have spurred fears of a STD outbreak.”UK surveillance data shows that sexually transmitted infection diagnosis rates are on the increase among all age groups in the UK,” said Catherine Mercer, lecturer at the Centre for Sexual Health & HIV Research, University College, London, who led the study.

The incidence of STDs in UK increased by six percent in last year as compared to figures in 2006. In a particular area of England, the STD rate more than doubled between 1996 and 2003.

Most Britons who don’t use condoms are in their thirties and forties with partners having an age difference of five or more years, according to the survey, said a report by Steven Reinberg in HealthDay reporter.

“Low rates of condom use among those starting partnerships in their 30s and 40s means that they too are at great risk of sexual infections,” Mercer said.

Mercer’s team based their study on more than 11,000 men and women who took part in the second British National Survey of Sexual Attitudes and Lifestyles.

The survey queried them on recent relationships, condom use and how soon they had sex.

Almost 9,600 people admitted having heterosexual sexual partners over past 12 months. More men (39.1 percent) than women (20 percent) said that these relationships were “not regular,” the researchers said.

One in five men said they had sex within 24 hours after meeting their partner compared with one in 10 women.

For example, between 16 to 19-year-olds, 68 percent of males and 67.4 percent of females used a condom during a first sexual encounter, while among 35- to 44-year-olds only 38.1 percent of men and 28.8 percent of women used a condom.

These findings were published Wednesday in online edition of the International Journal of Epidemiology.