Nearly 85% of those balloted support walkout, which would be third in union’s 101-year history.
Probation officers have voted by an overwhelming majority to go on strike in protest at government plans to privatise the service.
Nearly 85% of the members of the National Association of Probation Officers (Napo) who took part in the ballot supported the proposal. The turnout was 46%. No date has yet been set for the walkout.
Ian Lawrence, Napo’s general secretary, said: “We now have a mandate for industrial action that we shall be pursuing with vigour but as always Napo will be seeking to avoid this if possible by way of further negotiations with ministers.”
The justice secretary, Chris Grayling, is proposing to transfer most probation work to private firms such as G4S and Serco. If a strike goes ahead, it will be only the third time in its 101-year history that Napo will have taken such action.
A package of £450m-worth of contracts has been offered to private and voluntary sector organisations, covering the supervision of 225,000 low- and medium-risk offenders each year on a payment-by-results basis.
Contracts are to be split across 20 English regions and one Welsh region, while the National Probation Service, a new public sector organisation, will be formed to deal with the rehabilitation of 31,000 high-risk offenders each year.
Responding to the ballot, the justice minister Jeremy Wright said: “This is a strike in favour of the status quo, which is high reoffending rates and no support for 50,000 short-sentenced offenders each year who are currently released without any supervision and go on to commit so much crime in our communities.
“More than 600,000 offences were committed last year by those who had broken the law before, despite spending £4bn a year on prisons and probation. The public deserves better and we are committed to introducing our important reforms, which were widely consulted on.”