The announcement came just weeks after the electricians demanded a £5,000-a-head bonus for finishing the job.
But Balfour insisted the redundancies were part of a long-term plan and unconnected to the bonus issue.
A Balfour spokesperson said: “As works on the Crossrail Woolwich site wind down, we are beginning to demobilise our site operations and reduce our workforce.
“We have always been clear that our works would start to wind down towards the end of this year.
“On 8th November, we commenced a 45-day redundancy consultation period with Unite regarding the Balfour Beatty Kilpatrick workforce on the project.
“We made it clear that 50 to 60 operatives would be released from the project before Christmas.
“Yesterday, these employees were informed they would commence gardening leave as of today with their employment ending on 22 December 2017.
“We have of course explored alternative opportunities for the affected workforce but unfortunately on this occasion we have been unable to redeploy across our existing project portfolio.
“Today, a group of employees have assembled on site to protest about the redundancy consultation.
“This has not impacted our on-going works on site. We respect people’s right to have their say and protest peacefully.
“Our priority is to keep people on and around the site safe including our workforce, and the local community.”
Rank and file workers disputed Balfour’s claim that the protest had no impact.
One said: “150+ workers refused to cross the picket line at Woolwich station this morning in solidarity with sparks laid off by Balfour Beatty while 70+ workers walked off site at the Plumstead, City Airport & North Woolwich portals.”
Another added: “Solidarity to those on the picket lines. See you tomorrow morning.”