Police monitored the protest
Hundreds of energy industry contractors have walked out at sites in northern England and Scotland in an escalating protest over the use of foreign labour.
The dispute began at the Lindsey Oil Refinery, North Lincolnshire, on Wednesday after a construction contract was awarded to an Italian firm.
Unions said the contract should have been given to British workers.
In a second day of action, 800 people protested outside the refinery as workers from other sites joined them.
Hundreds of contract workers at the neighbouring Conoco Phillips oil refinery took part in Thursday's action.
Employees at BP's Dimlington gas terminal in East Yorkshire and its chemical manufacturing plant in Saltend, Hull, also walked out in support of the Lindsey refinery workers.
Unofficial strike action was also taken by workers at Scottish Power's Longannet power station in Fife.
Total, which owns the Lindsey refinery, said its main refining operations on the 500-acre site remained unaffected by the action.
It also stressed that there would be no direct redundancies as a result of the construction contract being awarded to Italian-based contractor IREM.
Unite union regional officer Bernard McAuley said workers at the refinery had been joined by hundreds of trade unionists and other supporters from around the UK.
He said: "They've come from all over the country. We reckon there were almost 1,000 people here today.
"We've also had huge numbers of messages of support from people who are incensed by this decision. It's a total mockery.
"There are men here whose fathers and uncles have worked at this refinery, built this refinery from scratch. It's outrageous."
The action was set to continue outside the refinery gates on Friday morning, the union said.
Total said in a statement: "We recognise the concerns of contractors but it is important to note that there will be no direct redundancies as a result of this contract being awarded.
"We have been a major local employer for 40 years and have always enjoyed a good relationship with our staff and contractors.
"We are disappointed they have taken this action and we hope the situation will be resolved as soon as possible and the contractors return to work."