Sexually active older Australians are contracting chlamydia and gonorrhoea in rapidly increasing numbers, as many shun condoms or feel too embarrassed to talk about safe sex, say experts.

New cases of chlamydia among Australians aged 40 to 85 have jumped 17 per cent in the past three years, while the incidence of gonorrhoea has risen 44 per cent in the same period, an analysis by Family Planning NSW reveals.

On the up: STI rates among the over-50s. Credit:AFP

Family Planning said 5563 new Australian cases of chlamydia were reported last year among people over 40 - about 33 people in every 100,000 - compared with 4733 new cases of chlamydia identified in 2010.

The figures show two cases of chlamydia among older men for every case reported for women.