The public sector has traditionally backed Labour because of its commitment to funding public services. But is this being tested because a growing number of public sector managers including teachers, senior social workers, NHS and council middle management find themselves in the same 40% tax bracket as those on £145k?

The faultline emerged last week when Labour's leadership split over the Budget plans to raise the level at which 40% tax kicks in from £46,351 to £50,000. The normally doctrinaire Shadow Chancellor John McDonnell argued pragmatically that Labour should support the tax changes otherwise it would lose the support of middle-class voters and higher paid public sector staff. But 20 Labour MPs voted against the tax changes saying they benefited the wealthy and furthermore it was a mistake to assume only the very rich should fund public services when everyone benefited.