Strike action across England this week will see unprecedented disruption to NHS services, England’s top doctor has warned today.

Professor Sir Stephen Powis said that it had been a challenged bank holiday weekend for hospitals in England and that the industrial action by junior doctors, starting at 7am tomorrow, would bring ‘immense pressure’ on services.

The junior doctor walkout begins at 7am on Tuesday and will not end until the morning of Saturday 15 April, which is the most extensive action on record.

Junior doctors make up around half of all doctors in the NHS – they are qualified doctors who have anywhere up to eight years’ experience working as a hospital doctor, depending on their specialty, or up to three years in general practice.

To make sure safe care continues to be available for those in life-threatening situations, NHS staff will be asked to prioritise emergency and urgent care over some routine appointments and procedures.

Appointments and operations will only be cancelled where unavoidable and patients will be offered an alternative date as soon as possible.

The NHS has said that people who need care must still access the care they need in the usual way – only using 999 and A&E in life-threatening emergencies and using NHS 111 online and other services for non-urgent health needs. Pharmacies and GPs are largely unaffected by the strikes so patients can still get appointments and health advice.

Professor Sir Stephen Powis, national medical director for the NHS in England, said: “The NHS has been preparing extensively for the next set of strikes but managing additional pressure doesn’t get easier as time goes by – it gets much more difficult – not only due to the sheer number of appointments that need to be rescheduled but also that they can take time to rearrange with multiple teams involved.

“This is set to be the most disruptive industrial action in NHS history, and the strikes tomorrow will bring immense pressures, coming on the back of a challenged extended bank holiday weekend for staff and services. Emergency, urgent and critical care will be prioritised but some patients will unfortunately have had their appointments postponed – if you haven’t, please do continue to come forward.

“As ever, use 999 and A&E for life threatening emergencies but use NHS 111 online for all other health conditions.”