The proposal was due to be announced by the Royal College of GPs.
It echoes the red and black alerts that hospitals use when they have more patients than they can manage.
The system would allow practices to stop taking new patients or call for help when they cannot manage the volume of patient appointments.
College leaders say that many GPs and their staff are facing extreme pressure and fatigue.
Chair Dr Maureen Baker said: "Few of us would voluntarily board a plane flown by a visibly tired pilot or get on a train where we knew the driver had spent too much time at the controls - yet there are no methods or systems for addressing doctor and staff fatigue in general practice.
"Our intention is not to panic patients but to send out a pre-emptive strike to ensure that we take steps now to protect patients from the risks arising from doctor and staff fatigue."
The government has put itself in conflict with consultants by accusing some of charging high rates for working at weekends and in the evenings because of their "opt out" clause.
But the British Medical Association yesterday highlighted the proposals for junior doctors, set out in last week's Doctors and Dentists Review Body report.
This would extend the standard working week for junior doctors to Monday to Saturday - rather than being Monday to Friday.
It would also extend the normal working day from 7pm to 10pm.
The changes would mean that doctors would not attract any antisocial hours payments for working on Saturdays or before 10pm.
The proposal is in support of the government's proposals to create so-called 24/7 working in the NHS - and would enable employers to put doctors on rotas for routine duties on Saturdays.
A BMA spokesman said: "The BMA opposed any extension to plain-time hours for junior doctors during contract negotiations.
"Junior doctors routinely work outside of plain time and are committed to continue doing so in order to provide their patients with high-quality care around the clock.
"However, evenings and weekends are precious opportunities to spend time with friends and family and it is only fair that doctors’ pay reflects this when work requires they lose this free time."
The unit in North Wales was closed in February as local managers cited a shortage of obstetricians.
The British Medical Association says the closure came in spite of proposals from consultants based locally to keep the unit open.
It brought a judicial review against the decision and now Betsi Cadwaladr University Health Board has withdrawn its opposition to the court case.
This will mean a six-week consultation on the closure is undertaken.
The BMA argued that women from the district faced a two hour trip to Bangor or Wrexham to see a consultant as a result of the closure.
The board has also been ordered by a judge to pay the BMA's costs of £105,000.
GP Dr Annick Cummings, from Prestatyn, said: "Nobody could understand why they wouldn’t take the hand that was offered because it was very clear they hadn’t followed their own procedures and the judge was quite clear she would be very keen for them to accept that offer.
"Despite that, they pushed forward for the judicial review. It is a great shame because it would have saved a lot of money for the health board and the money would have been better spent on patient care."
The General Medical Council said it had so far refused to licence some 770 doctors from Europe because they could not provide evidence of their ability to speak English properly.
According to The Guardian, this represented some 45% of applicants from Europe.
GMC chief executive Niall Dickson said it now sought to ensure only doctors with a "high level" of English are able to practise in the UK.
He said: "Medicine is an increasingly mobile profession and we must have systems in place which not only make sure that UK-trained graduates meet the required standards, but that all doctors practising here have been examined and evaluated to the same high level."
He added: "This has been an important patient safety measure. Doctors must be able to speak English properly. The fact that we can now check on doctors coming to the UK from elsewhere in Europe is proving effective."