Calls from business leaders for patients to be able to register with more than one GP have been described by Midland medics as a "recipe for a medical mishap".
The CBI wants a major overhaul of family doctor services, amid claims that millions of working days are being lost under the current system.
It claims that by registering at more than one surgery people would be able to see a doctor closer to their workplace in a bid to speed up treatment, and cut the time lost to their employers'.
However, it is currently illegal to register with more than one GP in the NHS.
But if a patient signs up with a secondary, private practice, it is the doctor's responsibility to notify the existing family GP.
Last night two Birmingham doctors said the CBI's proposals could lead to miscommunication between practices and hospitals, confusion over who is responsible for the patient, and a higher risk of clinical errors.
Dr Andy Thompson, who is based at the Enki Medical Practise in Handsworth, said: "It's hard enough when patients don't under-stand what medication they are on and there is often miscommunication between hospitals and GPs.
"Encouraging patients to register with several different doctors is a guaranteed recipe for a medical mishap.
"What the CBI is effectively saying to its members is that employers should not be allowing their staff to look after their health, which is a very dangerous position for them to take.
"The idea that GPs are difficult to access has been fully flouted by a recent Government report. But that is only good news if employers allow workers the time to go and see their doctor."
John Cridland, deputy director-general of the CBI, said changes were needed to tackle the 175 million days being lost every year because of ill-health.
"We need a GP service that fits around people's lives, offering convenience and flexibility," said Mr Cridland.
The organisation's report, Just What The Patient Ordered, said more over-the-counter advice from pharmacists would help break the link between where people lived and their access to healthcare.
It called for a number of changes, including:
* Steps to make it easier for patients to switch their GP.
* The ability to register at more than one GP practice.
* More primary care services available over the counter from qualified pharmacists, walk-in centres or other sites such as stores or railway stations.
* New providers being able to enter the market to deliver services in areas with too few doctors.
But Dr Fay Wilson, medical director of the Badger Medical Centre in central Birmingham, said the CBI was only interested in its "own commercial wealth".
"Legally it is currently not possible to be registered with more than one GP, and I don't see that position changing any time soon," said Dr Wilson, who is also the BMA's spokesman in Birmingham.
"It is quite common in London for companies to pay for private GPs to visit employees at work, which is one way around the problem. But this proposal, if it were to be implemented now, would be asking for trouble.
"I don't think they've got their employees' best interests at heart, their only concern appears to be with their own commercial health."
A survey of 1,000 adults conducted by the CBI showed one in three found it difficult to book an appointment with a doctor at a convenient time, with the business group warning people could be off longer than necessary as a result.
Mr Cridland added: "Billions of pounds of taxpayers' money is being spent on a GP system which seems unable to respond to patients' needs.
"Official figures show 10 million adults in England alone cannot book an appointment with a GP more than 48 hours in advance. It is time there was real and fundamental reform with the needs of the patient coming first."
A separate study of 200 doctors by high street giant Boots suggested 3.5 million working days are lost every year because of time spent at the doctor's, more than four times as much as is lost to industrial action.
Boots is testing a scheme in which GPs are based in the chain's pharmacies.
A walk-in centre, where shoppers could see a doctor or nurse, was based in Boot's High Street branch in Birmingham, but has since closed.
Dr Wilson added: "The walk-in centre at Boots was a good idea, but that was closed because people weren't prepared to pay for care they could get for free from their own GP."