People will still be able to see a family doctor out of hours if they need one, ministers have pledged.
Family doctors no longer have to provide out-of-hours services
New guidelines on who will provide out-of-hours doctor services in England have been issued by the government.
Under the new system, responsibility for organising night-time and weekend care will formally pass from GPs to primary care trusts (PCTs).
This will mean greater involvement by paramedics and nurses dealing with out-of-hours cases alongside GPs.
However, ministers stress family doctors will continue to visit the sick in their own homes out of hours if necessary.
The new guidance stipulates that "patients will be treated by the clinician best equipped to meet their needs, in the most appropriate location."
It also states that services will be regularly audited to ensure that patients are receiving quality care.
Thursday's announcement comes amid fears the changes might leave some areas without adequate night and weekend cover.
It emerged last month that 200,000 people in part of Lincolnshire had no direct access to a GP overnight.
And it has been suggested that doctors might need to be drafted in from places such as Germany to provide enough out-of-hours cover.
In the past, many GPs were unenthusiastic about working outside normal office hours, despite the fact they could be paid £6,000 a year extra to do so.
Since April, they have been entitled to opt out of providing out-of-hours services, under the terms of the new GP contract.
In practice, many GPs have been contracting out the services to other providers for some time.
But until now, the responsibility for organising cover remained with GP practices.
Health Minister John Hutton said: "Patients are entitled to expect the NHS to provide high quality, accessible and comprehensive primary care services during the evenings and at weekends.
"I am determined that this will continue to be the case once the responsibility for organising out-of-hours services transfers from GPs to PCTs this year.
"GPs will continue to play a leading role in helping to deliver out-of-hours services and working alongside nurses and other practitioners will help ensure patients get the right service at the right time from the right person."
Dr Hamish Meldrum, chairman of the BMA's General Practitioners Committee said: "We support the fact that patients are entitled to high quality services out-of-hours and believe that these new quality requirements will help to guarantee that.
"We do believe that where patients need to see a GP out of hours, a GP should be available."
Dr Mayur Lakhani, chairman-elect of the Royal College of GPs, welcomed the changes, but said it was essential that people could still see a doctor when they needed one.
He said using nurses or paramedics to assess patients was a "reasonable" option but said they should be part of a team which included GPs.
Dr Michael Dixon, chairman of the NHS Alliance, which represents primary care trusts, said the changes should make the service more responsive, as it would not be relying on doctors who were tired at the end of a hard working day.
He admitted finding enough staff to cover the out-of-hours shifts could be a problem - particularly in rural areas.
But he said: "I think in time we'll develop a workforce of people who like doing night-time duties and are probably better paid for it than some of the daytime doctors
Rebecca Rosen, of the independent thinktank, the King's Fund, said the new system could be improvement - if properly introduced.
But she said: "We are now left with a situation where patients and the public are justifiably confused about whether or not.
"Patients need to have confidence in the new system and there is a danger they will use A&E services as a default option if this crucial reorganisation is mishandled."