RISKY sexual practices and a reluctance to settle down with one partner have led to an increase in chlamydia detections across the Sutherland Shire.

Health authorities have found young people are increasingly likely to have unprotected sex with multiple sexual partners, putting them at risk of contracting sexually transmitted infections.

Marty Janssen, a social worker at Short Street Centre in Kogarah, urged people to get tested during Sexual Health Week (September 17-23).

Statistics for the Sutherland Shire showed the number of men diagnosed with chlamydia has doubled since 2008. There was also a large increase in cases among women.

If left untreated, chlamydia can damage reproductive organs, leading to chronic pelvic pain and infertility in both men and women.

Mr Janssen said the spike in results was partly due to more people being tested for sexually transmitted diseases and partly due to a rise in chlamydia in the community.

He said behavioural changes could also be behind the increase.

If you need information on testing call the NSW Sexual Health Information Line, 1800 451 624.