French oil company Total said on Friday that 1,200 contractors have walked out on unofficial strike over planned redundancies at its British Lindsey refinery.
Total said in a statement that 600 workers were protesting outside the refinery, but also claimed that production was not affected by walkout of over 1,000 of its workers.
The dispute centres around plans to reduce the number of contractors who have been working on an expansion project at the refinery.
Total said it had sent letters to 65 workers that they were at risk of redundancy "as the mechanical stage of the project which these contractors are working on is about to be completed".
"This is a normal process in the construction industry."
The Lindsey oil refinery in eastern England processes about 223,000 barrels of crude oil per day. It was at the centre of a wave of unofficial strike action in January by contractors over jobs.
Total said it was in talks with unions to try to resolve the situation as soon as possible. A spokesman for the GMB said the union was supporting efforts by the conciliation service Acas to hold talks to try to resolve the latest dispute.