The GMB union said workers were angry at a pay award of 4% which it described as a "massive real terms pay cut".

Emergency callouts would not be affected by any action, it added.

The government, which said it had given pay rises to more than a million workers, is urging ambulance staff to consider the impact on patients.

GMB acting national secretary Rachel Harrison said: "Ambulance workers don't do this lightly. This would be the biggest ambulance strike for 30 years.

"After more than 10 years of pay cuts, plus the cost-of-living crisis, workers can't make ends meet. They are desperate".

The GMB union previously said any action could take place before Christmas.

NHS workers in other unions, including nurses, are also being asked if they want to take strike action over pay.

'Safety and standards'

Ms Harrison said: "Without significant increases in pay, NHS workers and ambulance workers will continue to leave the service for higher paid jobs elsewhere.

"It can't continue, working under the extreme pressures that they are doing. This is more than just about pay, this is about patient safety and standards as well."

The Department of Health and Social Care (DHSC) said it had set out a range of measures to help ease ambulance pressures, including an extra £500m to speed up discharge and free up hospital beds, reducing waits in A&E.

This was, it said, alongside NHS plans to boost capacity and resilience ahead of winter, including increasing the number of NHS 999 and 111 call handlers.

It insisted it valued the "hard work" of NHS staff and had given more than one million workers a pay rise of at least £1,400 this year.

A spokesman said: "Industrial action is a matter for unions, and we urge them to carefully consider the potential impacts on patients."

Ambulance workers from the following trusts are taking part in the vote, which closes on 29 November:

* South Central Ambulance Service

* South East Coast Ambulance Service

* South West Ambulance Service

* East of England Ambulance Service

* East Midlands Ambulance Service

* London Ambulance Service

* North East Ambulance Service

* North West Ambulance Service

* Welsh Ambulance Service

* West Midlands Ambulance Service

* Yorkshire Ambulance Service

The DHSC said NHS England would work with providers, professional bodies and trade unions to agree the safe level of cover during any industrial action.