Government plans for a "one size fits all" contract for GPs could force more of them to retire early and worsen a recruitment crisis, West Midlands doctors have warned.
The claim was made as GPs from across the city prepare for a meeting tonight to discuss the proposals to extend their hours and open privately-run health centres.
Family doctors across the West Midlands have condemned the plans, claiming the move will ultimately damage patient care and, if practices opt-out, cost them about £36,000 a year.
GPs are currently contracted to provide patient services from 8am to 6.30pm, Monday to Friday.
Members of the Birmingham Local Medical Committee (BLMC) and the British Medical Association's West Midlands GPs Committee also fear calls for each PCT to open a new health centre that may be privately run by firms like Tesco and Virgin would "destabilise established practises".
More than 200 Birmingham GPs are set to meet at the Clarendon Suites, in Edgbaston, tonight to discuss the proposals.
Dr Robert Morley, executive secretary of BLMC, said: "The Government is trying to force an illogical 'one size fits all' contract on to all the nation's GP practices.
"What a minority of patients in other parts of the country demand is not what most of our patients need and want.
"Surgeries may have to limit their day-time appointments in order to provide appointments in the evening, which will directly affect this group of patients.
"Many vulnerable older patients can access our surgeries only by relying on transport facilities which may not be available at later hours. Some of these patients, quite justifiably, also fear for their safety after dark."
He added that support services such as pharmacies and laboratories would not be available, meaning patients would have to return during normal surgery hours, putting added pressure on practices. This could force many GPs to bring forward their retirements and further exacerbate the city's chronic shortage of GPs," said Dr Morley.
Dr Grant Ingrams, a Coventry GP and member of the BMA's GP committee, said there was an "unprecedented level of concern" over these issues.
NHS West Midlands, the region's strategic health authority, said extending GP surgery hours would improve access to services in "under-doctored areas".
A spokeswoman said: "We are responding to what our patients are telling us and that they want more flexibility around opening hours."
* The Conservatives submitted requests to NHS trusts last November to reveal the highest hourly rate paid to an agency worker over the previous 12 months.
The highest figure produced for clinical staff was £121.59 an hour for a nurse at the Royal Berkshire NHS Foundation Trust, followed by £121.10 for a nurse at Chesterfield and Royal Hospital NHS Trust.
Highest hourly rate for a non-clinical worker was £119 for a turnaround director at Coventry Teaching Primary Care Trust, followed by £110 for financial staff at Heatherwood and Wrexham Park Hospitals NHS Trust and £106.66 for a director of healthcare and procurement at Havering PCT.
Bath and North East Somerset PCT, however, said the most it paid was £31.15 per hour for a nurse, while the South Western Ambulance Service NHS Trust's most expensive agency worker was a temporary deputy finance director at £33.33 an hour.
Average NHS staff pay for a nurse is currently £30,531 a year, for a junior doctor £47,073 and for a consultant £117,610, according to Department of Health figures.