Unite organised the strike ballot for the workers who provide vital maintenance across the entire M25.

Balfour has offered them a 3.4% pay rise which has been dismissed as “meagre”.

Unite confirmed the strike vote on the day Balfour released its latest results showing a pre-tax profit of £244m from a turnover of nearly £10bn.

Unite general secretary Sharon Graham said: “Providing these workers with a fair pay rise would not even dent Balfour Beatty’s huge profits. Balfour Beatty is hugely profitable – its pay offer is all about greed not need. Unite will be backing our members 100 per cent during the forthcoming strike action.”

The workers operate from depots based at Barnet, Uxbridge, Swanley, Epping and Dartford and strike action will cause serious disruption to journey times.

Dates for industrial action will be announced in the coming days.

A Balfour Beatty spokesperson said: “We are disappointed by Unite the Union’s decision to proceed with strike action. We remain committed to working with them to reach an appropriate outcome, and would like to reassure travellers that suitable contingency plans are in place to minimise any potential disruption”.

Unite regional officer Phil Silkstone said: “The inconvenience and delays caused by strike action to M25 travellers sits squarely at the door of Balfour Beatty. It has had every opportunity to put forward a reasonable offer but has repeatedly refused to do so. Balfour Beatty must swiftly return to talks with Unite and table an acceptable pay deal.”