NHS staff are due to hold a four-hour strike over pay this morning from 7am to 11am.
The strike is being held because of the decision not to give all staff the pay rise recommended by an independent review.
Unions, including Unison, Unite and the GMB, said that patients needing emergency care would not be affected.
But the action is likely to affect outpatient appointments and could mean delays to non-emergency surgery.
Six days of working to rule are planned during which union members are expected to take their breaks rather than work through them. They may also refuse to work overtime and claim pay for any extra hours that they do work.
The action comes after unions held a four-hour strike on Monday 13 October which was the first relating to NHS pay for more than 30 years.
The unions organising the strike today are
British Association of Occupational Therapists
Managers in Partnership
Prison Officers Association
Royal College of Midwives
Society of Radiographers (on strike from 8am to noon)
Union of Construction, Allied Trades and Technicians
Two others may take action short of a strike for six days from tomorrow (Tuesday 25 November) – the British Dietetic Association and Hospital Consultants and Specialists Association.
The pay dispute arose because the government ignored the results of an independent pay review which recommended a 1 per cent rise for all staff.
Ministers awarded staff a 1 per cent rise if they did not receive an automatic pay rise as part of their contract.
The Department of Health said that it could not afford to implement the pay award without putting jobs at risk.
A similar review recommended awarding MPs a 10 per cent pay rise which is being implemented.