The number of gonorrhoea cases reported in NSW has more than doubled and incidences of chlamydia and syphilis have also spiked in the past four years.

The number of sexually transmitted infections reported in NSW has skyrocketed over the last four years, despite the state government's commitment to reducing cases.

The three infections targeted in the NSW STI Strategy 2016-2020 - gonorrhoea, chlamydia and syphilis - have all experienced large increases.

Between 2014 and 2018, the number of gonorrhoea cases reported increased by 110 per cent - from 4835 to 10,164.

Over the same period, the number of syphilis cases reported jumped by 79 per cent and the number of reported chlamydia cases rose 35 per cent.

The infections can cause infertility, meningitis, birth defects in children and other serious health problems.

NSW Health said the spike in notifications was in part due to increased and well-targeted testing, as the STIs can present without symptoms and may go unreported.

While the number of notifications per 100 tests for chlamydia has remained stable over time, the rate of gonorrhoea has gone up 60 per cent since 2014.

The same measure is not recorded for syphilis.

"NSW Health is committed to decreasing the incidence of STIs and is currently investing $21.9 million in services to strengthen HIV and STI testing, treatment and prevention, including $1.5 million in sexual health programs for young people aged 16-29," a department spokesman told AAP.

One of the strategies is to encourage general practitioners to incorporate STI screening as a part of routine care, he said.

The STI Strategy, launched in 2016 by then health minister Jillian Skinner, hoped prevention programs and more testing targeting vulnerable populations would see a reduction in the spread of STIs.

NSW Health Minister Brad Hazzard declined AAP's request for comment.