Restricting access to contraception could cost the NHS £125 billion in less than 10 years, a damning report from health charities has claimed.
Including increased spending on housing and education, the government could be paying out £136 billion by 2020, the report, Unprotected Nation said.
NHS efficiency savings are "undermining the quality" of services by creating a "postcode lottery", it has been claimed.
Disruption through changes to the commissioning structure have also been blamed in sexual health charity Brook's and the Family Planning Association's (FPA) joint report.
Simon Blake OBE, Brook's chief executive said: "The national sexual health and teenage pregnancy strategies have ended and the NHS is under intense pressure to make savings.
"This report makes it very clear just how short-sighted restrictions to contraception services are."
The Unprotected Nation report claimed the restriction of sexual health services could lead to 91,600 more STIs per year by 2020.
Increased infection rates alone could add £314 million to the NHS budget, the report seems to show.
The report also found that 22,000 more abortions could be performed per year because of the "increasing number of unintended pregnancies".
"If national and local government ignore the warnings and continue stripping away services, advice and information, the bleak predictions in this report will come true," said Dr Audrey Simpson OBE, FPA's acting chief executive.
Dr Simpson said: "Unplanned pregnancies and sexually transmitted infections have obvious costs to people's health, but the financial costs to the NHS are also real."
Brook and FPA's joint report examined how much the government would have to pay if sexual health services were less accessible, more accessible or stayed the same.
The report found that if there is improved access to sexual health services, including advice, the government could save up to £5 billion by 2020.
Dr Anne Connolly, chair of the Primary Care Women's Health Forum said: "There is a clear danger that imminent changes to commissioning could significantly undermine the good work being done.
The GP added: "Maintaining progress requires investment and if we are brave enough to invest money at a time when there is pressure to disinvest there are massive cost savings as well as quality of life savings to be made."
Dr Tony Falconer, president of the Royal College of Obstetricians and Gynaecologists (RCOG) said: "In addition to high quality care provided in general practice, open access specialist services are required to meet the needs of all women.
"Access to contraceptive services must include emergency contraception and long acting reversible contraceptives (LARCs) which offer women greater protection against unplanned pregnancy."