The companies have rejected an offer to accept reduced pay rises in return for maintaining existing job security provisions as the Baird government prepares for the partial sale of the electricity network. On Wednesday, the Electrical Trades Union  notified the companies that Endeavour Energy staff will stop work for four hours on Tuesday. Ausgrid employees will hold staggered work stoppages on March 31, April 1, and April 8.

The ETU said minimum staff coverage will be maintained to ensure power supplies are not affected.

It said the industrial action will involve thousands of workers who operate and maintain the electricity network in Sydney, the Hunter Valley, Newcastle, the Central Coast, Wollongong, the Illawarra, Blue Mountains and parts of the Central West. ETU secretary Steve Butler said it had been forced to escalate the dispute after the publicly-owned power companies rejected their offer to accept a 2.5 per cent a year pay increase in return for job security provisions ahead of the government's privatisation plans.

"The Ausgrid and Endeavour workers who operate and maintain much of the NSW electricity network are justifiably concerned about their future job security given the Liberals and Nationals' plan to sell a majority stake in these public companies to private owners," Mr Butler said.

"Industrial action is always a last resort, especially when it involves an essential service, but power workers have been left no choice following the refusal of management at Ausgrid and Endeavour, or the NSW Government, to agree to provide job security ahead of Mike Baird's privatisation plan.

"Premier Mike Baird tries to claim a new private owner won't slash jobs and services at these companies, but his government is refusing to support an agreement that would put that in writing."