Women are finding it harder to access contraception than they did a decade ago, resulting in more unplanned pregnancies, the women’s health ambassador has said.

They have been discouraged by bad experiences, a confusingly disjointed system and long delays for procedures such as the coil or implant insertion, according to Prof Lesley Regan, a leading gynaecologist who was appointed women’s health ambassador for England last year.

She said that “destructive” changes made to the NHS commissioning system in England in 2012, which siloed GP surgeries from hospitals, were failing women. “If you’re not commissioned to deal with the problem, there’s no incentive to do a job properly … Contraception has got to be everybody’s business and up until this moment it’s been nobody’s responsibility and no one’s been accountable for it.”

She added that the NHS preoccupation with cost was counterproductive as “contraception is the single most cost-effective intervention in healthcare”. She is pushing to get the progesterone-only pill, which took a decade to become available over the counter, made free in pharmacies so fewer women “fall through the cracks”.

Faculty of Sexual and Reproductive Health research shows that 45% of pregnancies in England are unplanned, and one in four pregnancies ends in termination, according to ONS figures for England and Wales.

Regan hopes that the women’s health hubs, for which the government has earmarked £25m under the women’s health strategy for England, will improve the situation, partly by replacing the sexual health and family planning clinics, which have been cut. But she acknowledged the funding was “a drop in the ocean” and finding ways to train more GPs in contraception and dissolving the barrier between general practice, clinics and hospitals was also crucial.

“We have to get the funding much less stultified into these silos and say women have to get what they need and then wrap services around them. I don’t see why you need to go to four different appointments to get your HRT, your mirena [coil] changed, your smear test, when you could get it all done in one appointment,” she said.

She gave the example of someone who arrived at a special clinic for period problems. They could be given a mirena coil for painful or heavy periods, but would not be able to receive it for contraception, because that’s not what the clinic is commissioned for.

Regan was speaking as part of a Q&A with participants in Davina McCall’s new documentary, Pill Revolution. McCall is hoping to do for contraception what her documentaries in 2021 and 2022 did for the menopause, unleashing a “Davina effect”, which increased awareness of symptoms and treatments and resulted in a tenfold increase in NHS prescriptions for HRT.

McCall feels the current system – in which women struggle to access comprehensive information on options and their possible side effects, and use trial and error to find what works – is no longer fit for purpose.

She is hoping her documentary will prompt a “tsunami of interest and questioning” among women to build pressure for change and challenge the misperception that because contraception effectively prevents pregnancy there is no need for improvement. “We’re talking about a conversation that has to be a revolution,” she said, adding that at the end of filming the documentary she felt “really fucking angry but also full of hope”.

A survey of 4,000 women undertaken for the show found that 77% of women had experienced side effects after taking the pill, while 33% had changed their contraception as a result.

The documentary also looks at the barriers to accessing contraception. Dr Fran Yarlett, GP and medical director at The Lowdown, which features in the documentary, said that the pandemic had exacerbated long waits for contraception, with one study showing that the number of people unable to access contraception has increased from 0.6% pre-lockdown to 6.5% post-lockdown.

Freedom of information requests undertaken for the documentary showed that most women wait more than a month for an appointment to get their coil inserted, with longer delays in some parts of the country, including waits of more than a year in Devon and Northern Ireland.

Many women have become fearful of coil insertion after reading horror stories about pain. The documentary shows McCall having her mirena coil changed onscreen by Regan to demonstrate the procedure does not have to be painful, although McCall acknowledged she benefited from pain relief and a highly experienced practitioner.

In her bid to find ways for women to more easily find contraception that works for them, McCall visited Dama Health, a startup that is looking to create a test that establishes whether women have a genetic susceptibility to certain side effects.

She was exasperated that it should take a private company to do this: “The really big thing that’s come out of every documentary that I’ve made is the massive black hole that is there where research into women’s health should be,” McCall said.

A Department of Health and Social Care spokesperson said: “We published a women’s health strategy for England and recently announced £25m for women’s health hubs – enabling women across the country to benefit from better access to care for essential services including contraception.

“It’s now easier for women to access contraception through the NHS Pharmacy Contraception Service, with pharmacists able to supply oral contraception without the need for a prescription from a GP.

“We’re also providing more than £3.5bn this financial year to local authorities to fund public health services – including sexual and reproductive health services. This will increase to £3.58bn in 2024-25.”

Davina McCall’s Pill Revolution will be shown on Thursday 8 June at 9pm on Channel 4.