Speaking at the NEU’s conference, in Bournemouth, general secretary Daniel Kebede said there was “more and more frustration developing amongst” teachers.

“My view is if there is a decision to go for a formal ballot, we should conduct that over a fairly significant period of time, looking to take action in September,” he said.

Members have already been asked if they would strike for a fully funded above-inflation pay rise, as part of an informal consultative ballot in recent weeks.

And in England and Wales, most responded, with about 90% saying they would be prepared to strike – a result Mr Kebede called “exceptionally significant”, adding England’s Education Secretary, Gillian Keegan, “has to take that seriously”.

NASUWT, the Teachers’ Union, also held an informal consultative ballot, in England – but 78% of those who voted rejected a formal ballot.

General secretary Patrick Roach told its conference, in Harrogate, N Yorks: “Our members have weighed that up and their priority right now is not about causing more disruption to lives that are already in tumult, but actually saying we need a government that’s on the side of teachers and on the side of children and young people.”

The union would be “looking carefully at how the government responds” to calls for a pay rise, he said, adding: “2023 was a year of action – this must be the year of change.”