Main civils contractor Bouygues and Laing O’Rourke (BYLOR) is proposing the new shift working arrangement.
Workers complain that the new plans would leave them out of pocket.
One said: “On the new eleven on and three off shifts they are proposing, we would lose half a day’s pay, as the site shuts early on a Friday.
“However, you can come in on a Saturday if you like, to make up the hours. Nobody is going to agree to this.
“We’d be working over an hour less a day on day shift, as it’s only 9 hours, as opposed to the 10.5 hours we are getting now, on standard five and two shifts.”
“This would mean we would earn less over the two week period, than we currently earn, and would be giving up a weekend to do so.”
He added: “Kier/Bam have already gone onto an eleven and three shift system, and some are down almost £600 per month on their earnings.”