Unite has staged a series of protests at the Euston site where a Costain/Skanska joint venture (CSJV) is in charge of enabling works.
The union claims officials are not being allowed into the site canteen and welfare areas during break times to discuss working conditions with operatives.
The job has already been hit by a pay row over overtime rates and has become a focus of Unite action in construction.
The Enquirer has now seen an email sent by union officials to CSJV employment chiefs proposing ‘peace at Christmas’.
It offers to suspend all planned December demonstrations “in exchange for all workers on the project being given a Christmas turkey.”
The union is suggesting workers are given a £25 supermarket voucher to pay for the festive birds rather than flooding the site with fowl.
The email adds: “I realise this offer has come somewhat out of the blue but hopefully even CSJV will find themselves gripped by Christmas and able to show good will to all men and women.
“Should you be agreeable to this suggestion, you never know we may during this cessation find a solution to the current issues.”
CSJV has been contacted for a comment.