Research suggesting that one in four evening and weekend GP appointments in England are going unfilled has been described as “shocking” by critics of the government’s controversial drive to guarantee access to family doctors at weekends.

Around half a million appointment slots have been left empty on evenings and weekends, according to data obtained under the Freedom of Information Act (FOI) from 80 clinical commissioning groups (CCGs).

Take-up was at its lowest on Sundays, when 37% of appointments go unfilled, according to figures obtained by Pulse, a specialist publication for doctors. On weekday evenings, 23% of slots were going unused.

The figures were seized on by the British Medical Association, which opposes the government’s ‘seven days a week’ pledge on doctors’ appointments at a time when waiting times for routine weekday appointments are lengthening. However, officials at NHS England believe the figures could be used to show the policy is popular and that take-up will continue to grow as the public becomes more aware.

The government has promised to ensure that people in every part of England will be able to see a GP from 8am to 8pm every day of the week as a key element of its push to create a “truly seven-day NHS” by the end of the current parliament. Under NHS guidance from earlier this year, Monday was set as a date by which CCGs were required to provide extended access to GP services.

However, the chair of the Royal College of General Practitioners (RCGP) said it was “shocking” that so many appointments were going unused.

Prof Helen Stokes-Lampard said: “GPs want to give patients access to services they need but this will differ depending on local demographics.

“At a time when general practice is struggling for resources and patients are waiting longer for routine appointments, to find out so many evening and weekend appointments have been unfilled due to lack of demand is shocking.”

Dr Richard Vautrey, the BMA GP committee chair, said: “Because it has become a political must-do, everybody is jumping. We understand there is huge pressure from the centre on CCGs to demonstrate they are providing a full seven-day service.

“Sensible CCGs that want to use their resources in a better way are under pressure to maintain a service that really isn’t good value for money.”

An NHS England spokesperson said: “Despite this small survey of a minority of the country, patients do actually want to be able to see a GP at convenient times, and that includes evenings and weekends.

“To suggest that people should always be forced to take time off work if they need to see their GP would be a backward step, and as the popularity of new types of online digital primary care shows, patients are increasingly prepared to vote with their feet to get convenient access.”

Pulse said it had estimates that at least £15m has been “wasted” on the total of 501,396 unused extended hours slots across the 80 CCGs that responded to FOIs. This was based on NHS England’s evaluation of the scheme’s pilot.

Among the bodies that responded, NHS Thanet CCG in Kent indicated it had seen patients book 3% of available appointments on Sundays and 26% on Saturdays since April 2018.

A CCG spokesperson said: “We are working with our team to ensure there is a publicity campaign across east Kent prior to the national 1 October go-live date. Our expectation is that uptake will improve once awareness increases and will build with time.”