Ambulance staff across south-west England have voted overwhelmingly for a ballot on industrial action following a dispute over night cover.
Unison claims cover in some rural areas will be reduced
Unison members with Westcountry Ambulance Service were asked to comment on cuts in shift times, lower grade and part time staff and more lone working.
More than 600 ballot papers have been counted and 89% call for a vote on industrial action, says the union.
Officials say they have been astonished by the strength of feeling.
Plans to change emergency cover were confirmed last month by Westcountry Ambulance Trust, which says the changes will mean greater flexibility and more resources.
Under the changes proposed, more emphasis will be put on rapid response vehicles (RRVs) and emergency care assistants working on their own.
But union officials say that patient safety could be compromised by scaling down 24-hour cover and the use of RRVs will reduce cover in some rural areas.
Union members were asked to vote on four specific questions about changes to overnight cover.
Asked if they agreed with the employment and use of emergency responders replacing staff on meal breaks, 94% said no.
On the question of the trust employing staff with lower-grade qualifications to deliver immediate care to patients at any time, 89% voted against.
Responding to question three about the introduction of 10-hour shifts, with the consequent loss of cover, 86% said they did not agree with it.
More than 89% said they disagreed with the assimilation of different pay rates.
Those who disagreed with the questions have voted to be consulted about industrial action.
But despite the result of the ballot, Unison says any vote for strike action is unlikely, although it could not rule out some other form of industrial action.
Westcountry Ambulance Trust says until a union representative has officially presented the result, it will not comment.