No one knows how many GPs will be operating out-of-hours services when their obligation to do so ends after December 31, MPs said last night.
The uncertainty in staff and funding for the switch in responsibility for night-time and weekend medical cover had to be resolved so quality of care was not compromised, the all-party Commons select committee on health said.
Patients needed to be informed of changes in the system under which accessing such healthcare meant "negotiating a maze of different services and telephone numbers".
The British Medical Association has said more than 90% of GP practices will opt out, losing individual GPs about £6,000 a year, but it remains unclear how many doctors will choose to work out of hours under separate contracts.
Since April NHS primary care trusts have been taking over the service from GPs, although some will not until the deadline.
Twenty years ago most GPs provided their own emergency cover, but over the past 10 years many practices have formed cooperatives to spread the load, or contracted out-of-hours work to private companies.
New services are being designed using nurses, paramedics, social workers and mental health specialists as well as NHS Direct and doctors. In some cases walk-in clinics are being provided as well as home visits and telephone consultations.
But GPs are expected to provide the backbone of the reformed service and, according to the committee, supply the NHS's main expertise.
The committee's Labour chairman, David Hinchliffe, the MP for Wakefield, said: "Recruiting and training a new workforce will take time and investment and we argue PCTs take full account of this. Trusts should also work collaboratively with GPs to provide the flexibility and support as well as financial incentives necessary."
The government has provided some funds for the switch but many PCTs believe they will not have sufficient money. The Department of Health had to monitor this closely, Mr Hinchliffe said.
The MPs are also concerned at the closure of Saturday surgeries as a result of the changes and the effect that may have on A&E and ambulance services, if not managed properly.
