Thousands of 999 call handlers, ambulance technicians, paramedics and their colleagues working for ambulance services in the North East, North West, London, Yorkshire and the South West are due to be called out on strike over pay and staffing levels, Unison said.

However, the union said an exact strike date has not yet been set.

It said large numbers of its members had voted to take industrial action following a long-running dispute over pay and staffing levels.

The exact areas that will be affected have not been confirmed, as Unison said the vote was just below the 50% threshold in many trusts.

However, Sky News understands only eight employers out of more than 200 got over the threshold.

These are believed to be five ambulance trusts and two Merseyside hospital trusts.

Unison general secretary Christina McAnea said: "The decision to take action and lose a day's pay is always a tough call. It's especially challenging for those whose jobs involve caring and saving lives.

"But thousands of ambulance staff and their NHS colleagues know delays won't lessen, nor waiting times reduce, until the government acts on wages. That's why they've taken the difficult decision to strike."

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She added that, despite the strikes, patients will "always come first" and emergency cover will be available.

"The public knows health services won't improve without huge increases in staffing and wants the government to pay up to save the NHS. It's high time ministers stopped using the pay review body as cover for their inaction," she said.

What's happening across the rest of the UK?

The union's health committee is analysing the results of the ballot and will decide what happens next.

It follows a decision by up to 100,000 nurses from the Royal College of Nursing (RCN) to stage a mass walkout in December – one of the busiest months for the NHS.

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Health workers belonging to UNISON and working in Northern Ireland have also voted to take action over pay and staffing.

However, in Scotland, the union is recommending its NHS members vote to accept the latest offer from the Scottish government, which will see a £2,205 increase for the lowest paid staff, and more for those on higher bands.

Earlier this month, both Unison and the RCN were among several unions that met Health Secretary Steve Barclay to discuss the growing NHS "workforce crisis" and to urge the government to take action on wages.