Clinics offering women contraception are closing or reducing their opening hours in the wake of heavy Whitehall cuts to local councils’ public health budgets, new research has revealed.

One and a half million women of reproductive age live in parts of England where councils have restricted contraception services or are considering doing so, according to data obtained under freedom of information by the Advisory Group on Contraception.

The findings have prompted warnings from sexual health experts that paring back such services could lead to an increase in unintended pregnancies and abortions. One in four councils have already reduced their contraception service or may do so, the new findings show.

“Councils are between a rock and a hard place when faced with cuts to public health budgets, but it’s a false economy to restrict women’s access to contraception,” said Natika Halil, the chief executive of the Family Planning Association, which is a member of the AGC.

She cited research showing that every pound spent on contraception saved £11 in averted health costs, for example from women going on to have a baby or a termination.

“Making it harder for women to choose the right contraception for them will mean more unplanned pregnancies and more abortions,” she said.

Four sites offering contraception services have closed or will close during 2016-17 in Dorset and several clinics have stopped operating in Wandsworth in south London.

Responses from 140 of England’s 152 councils to the freedom of information requests showed that a lunchtime school drop-in service in south Gloucestershire has been ended, a sexual health worker in Wokingham in Berkshire lost their job when a condom distribution service was brought in-house by the council and a young people’s service in Bexley, south London, ceased being a standalone service but is now being provided in a local GP’s surgery.

Dr Anne Connolly, a GP in Bradford who sits on the AGC, said: “It’s hugely concerning to see that, in many parts of the country, contraceptive services are being cut, meaning that women can’t access the most reliable types of contraception. Without close scrutiny, I’m worried this trend will only continue and that women will bear the consequences.”

Among the 140 councils which responded, 20 (14%) confirmed that at least one site had shut in 2015-16 or would do so this year, while another 18 (13%) said that clinics could be closed this year. The AGC is made up of health charities such as the FPA, doctors, the Local Government Association and the Faculty of Sexual and Reproductive Healthcare, which represents specialists.

Councils in England have been obliged by law since the coalition government’s NHS shakeup in 2013 to provide open access to sexual health services, including for contraception.

NHS England commissions some contraceptive services under its contract with GPs. The AGC also found that fewer councils now have contracts with local family doctors to provide the long-acting forms of contraception that women are now often encouraged to use.

However, councils have had to reduce the public health services they offer since the Treasury cut £200m from their budgets for this year and it intends to take another £600m by 2020-21, just under 10% of the planned total.

Simon Stevens, the chief executive of NHS England, has warned several times that cuts to public health will inevitably lead to higher long-term costs for the NHS. Last year, he said he was “crystal clear that any further cuts in public health and social care would impose extra costs on the NHS over and above the minimum funding requirement [the £8bn extra by 2020-21 that then chancellor George Osborne promised last year to give the NHS]”.

The Department of Health said councils were best at deciding what public health services they provided for their residents.

“Local areas are best placed to decide how to provide the sexual health services their communities need. Good progress is being made, for example teenage pregnancy is down 30% in England since 2011, the lowest for 40 years”, a spokesman said.

“Over the next five years, we will invest more than £16bn in local government public health services, in addition to what the NHS will continue to spend on vaccinations, screening and other preventative interventions.”

• This article was amended on 13 December 2016. An earlier version said a sexual health clinic operating at Leighton hospital in Crewe, Cheshire, was shut down last year. It has been relocated to a nearby site.