A wildcat strike over jobs is escalating with workers from several power stations and oil terminals across the UK taking unofficial industrial action.
The dispute flared a week ago at the Lindsey oil refinery in Lincolnshire when a contractor laid off 51 workers while another employer on the site was hiring staff.
Around 1,200 contract workers at the Total plant have taken unofficial action all week.
Sources said workers at several other sites across the country were taking part in the action.
They include power stations at Drax and Eggborough in Yorkshire, Ratcliffe and West Burton in Nottinghamshire, Fiddlers Ferry in Cheshire and Aberthaw in South Wales.
Contractors at a BP refinery near Hull are also involved.
Paul Kenny, general secretary of the GMB union, said he had been in touch with the conciliation service Acas and was seeking an urgent meeting with the head of Total to try to break the deadlock.
The Lindsey refinery was hit by strikes earlier this year in a row over the recruitment of non-UK workers.