The HSE-run Building Safety Regulator requires all building control professionals to be registered and prove their competence by April 6 as part of the post-Grenfell industry shake-up.

At least 4,500 qualified inspectors are understood to be needed to cope with current workloads.

But trade body LABC is warning the government that nowhere near that number will be on board by April with the whole inspection system set to collapse unless there is a six month delay to registration plans.

LABC chief executive Lorna Stimpson has written to HSE and government chiefs warning that “local authorities will cease to be able to undertake a building control function post April 6.”

This will mean ongoing construction projects will not be inspected while stop and compliance notices will not also be served.

Stimpson added: “LABC is undertaking an urgent review of the position of all local authorities in England and Wales, to determine their position with regards to the number of surveyors likely to be certified and registered prior to the deadline – the picture does not currently look encouraging.”

One industry expert said: “Building control has been neglected and under-resourced for years but these changes look like they will tip the whole system into chaos.

“Experienced inspectors are retiring with no-one to take their place while the authorities have been sleep walking towards this deadline for ages without any thought as to how things will work in the real world.”