The growing number of sexually transmitted infections among over-65s, the rise of “chemsex” and popularity of dating apps are driving record demand for sexual health advice, a report has revealed.

Specialist advisers provided just over 4m appointments last year in England to people suffering from an STI such as syphilis or needing help with their contraception.

Attendance at sexual and reproductive health services is “skyrocketing” as a result of changes in people’s sexual behaviour, according to a report by the Local Government Association.

It highlights that the number of STIs recorded among over-65s increased from 2,280 in 2017 to 2,748 in 2019 – a 20% rise. The biggest increases were in gonorrhoea and chlamydia.

“Chemsex” gatherings, where predominantly gay and bisexual men have sex while taking drugs such as GHB and mephedrone, are heightening the risk of people becoming infected with HIV or hepatitis B or C.

“This has greatly impacted the volume and complexity of work that sexual health services are dealing with. Chemsex interactions have increased … and this has led directly to increased attendance at sexual health clinics, notably in cities/urban centres,” the LGA report said.

The widespread use of hook-up apps is also leading to more STIs. For example, among women, they have led to “greater risk-taking and thus far more likelihood of needing treatment for an STI”, according to the report’s authors, councillor David Fothergill, the chair of the LGA’s community wellbeing board, and James Woolgar, Liverpool’s director of public health.

“The high use and access to smartphones and dating apps comes at a cost,” the report said.

“Sexual mixing has changed considerably over the last 10 years, with a growth in the use of apps and online dating,” said Fothergill. “This, coupled with a small but growing number of people over 65 requiring support from sexual health services, has led to these services facing new and emerging pressures that they have had to tackle.”

The number of STIs diagnosed in England is falling; 311,604 were recorded in 2021. However, about 2 million people that year were tested for an STI, 19% more than in 2020.

Recent years have seen a huge increase in people who need sexual health advice accessing it online rather than at a clinic or over the phone, the LGA found. A large and fast-growing minority of the 4 million people services helped in 2021 were seen that way.

Dr Claire Dewsnap, president of the British Association of Sexual Health and HIV, said services are under unprecedented pressure because of “a wider evolving sexual health landscape”.

“Changing patterns of sexual behaviour amongst some demographics are being reflected for instance through increases in the levels of STIs diagnosed amongst those over 65, whilst practices such as chemsex and use of dating apps can also be associated with higher-risk behaviour,” she said.

The LGA warned that services, which are funded by local councils rather than the NHS, are “at breaking point” because, despite record attendances, they have had their funding cut as a result of the public health grant, which the government gives to councils, shrinking by about £1bn since 2015. Further cuts could hit efforts to reduce STIs, access to contraception and the drive to limit teenage pregnancies, Fothergill warned.

The number of women choosing long-acting reversible contraception (LARC) over the pill – coils, implants and injectable contraceptives – is rising dramatically. In 2011 just 29% of women attending a sexual health service did so to do with such methods of contraception. But last year that figure stood at 56%, the LGA said.

A Department of Health and Social Care spokesperson said: “We have provided more than £3.4bn this year to local authorities in England to fund public health services, including sexual and reproductive health.

“Local authorities are responsible for providing open-access sexual and reproductive health services, including free and confidential HIV and STI testing, condoms, provision of the HIV prevention drug PrEP, vaccination and contraception advice.”