There are more than 150 walk-in centres around England. The initiative by former Labour Minister Lord Darzi, who gave his name to the programme, was part of moves to improve access to GPs in more deprived areas, which usually have fewer doctors, and also to fit services around people's lives and give patients more choice.
Figures show each centre in Yorkshire was due to cost between 500,000-1.5m to run each year. But higher-than-expected costs due to their popularity are causing significant financial difficulties for primary care trusts which are only like to worsen in years to come as NHS funding is cut and already services are being axed barely a year after opening.
The first centre in the country was opened two years ago in Barkerend, Bradford, by former Health Secretary Alan Johnson.
NHS officials calculated 540 walk-in patients per month would use the service, open 8am-8pm every day of the year, by 2013 but already 1,530 are accessing it each month.
Health chiefs in the East Riding set up a centre in Bridlington as the town has higher levels of deprivation and poorer health compared to other parts of the area and high numbers of holidaymakers in summer months.
But demand for walk-in care has dramatically outstripped expectations, with more than 12,000 attending in its first year to June compared to original estimates of 1,800.
Surprisingly, it has not reduced demand at the minor injuries unit on the same site at the town's hospital but officials say lower numbers than expected of people formally registering with GPs as patients, which are only a third of levels predicted, have compensated for the higher costs of walk-in patients.
NHS Kirklees failed to provide a breakdown of figures of its Darzi centre in Dewsbury. But a report to its board reveals demand for the walk-in service was double that expected.
The increased demand put an additional 350,000 pressure on budgets which could rise to as much as 500,000 a year.
In a move to cut costs, the service was last month closed to walk-in patients on weekday mornings. Patients can expect to wait longer for care and non-urgent cases might also be turned away.Health chiefs in Barnsley said surveys had suggested a "high level of satisfaction" with existing access to GPs which led them to believe only 4,500 patients would use the walk-in centre in its first year.
But in practice nearly 21,000 had used the service, including as many as 100 on some days.
They said the value of the extra demand was equivalent to funding three large GP practices employing 18 doctors. The walk-in service was axed last month to save cash although the surgery remains open to see registered patients.
Overall, demand for walk-in appointments is at least twice that expected at more than half of the region's centres also including Grimsby, Scunthorpe, Halifax and Todmorden.
In Hull, officials were unable to provide figures but demand on some days is three times that expected.
Health chiefs in Wakefield also did not have details but said demand was higher than expected.
NHS Leeds said no targets were set for its service in inner-city Burmantofts. NHS Rotherham failed to provide any figures.
Demand for drop-in care is below target only at Sheffield's city centre practice in Broad Lane although changes from April will increase demand when a separate walk-in centre at the Royal Hallamshire Hospital is closed.