Unite members working for EDF Powerlink are to strike for four days from today, after last minute talks failed.
Members rejected a proposed two-year pay deal of 1.5% for 2009-10 and 0.5% for 2010-11, according to Unite. An open-ended overtime ban will also begin today.
Unite regional officer John Morgan-Evans said: “Our members have seen their pay slowly eroded over the years, and they are now making a stand.”
The workers maintain the electrical systems for London Underground, so there are concerns that their industrial action may force the closure of at least part of the Tube over Christmas.