Union Unite said the road workers are angry at Balfour’s pay offer of 3.4% following another below inflation pay rise last year.

Unite general secretary Sharon Graham said: “Balfour Beatty is an immensely profitable company that can afford to put forward an offer that reflects rising living costs. Its M25 workers have Unite’s total backing in demanding a fair pay rise.”

The workers will begin balloting this week and the vote will close on 12 March, with industrial action expected soon after.

Unite regional officer Phil Silkstone said: “Balfour Beatty can stop this dispute escalating and causing disruption to the smooth running of the M25 by tabling an acceptable offer. It has more than enough profits to do that.”

A Balfour Beatty spokesperson said: “We continue to work closely with Unite the Union to reach an appropriate outcome.

“As these discussions remain ongoing, it would be inappropriate to comment further at this time.”