Unite the Union members working for Aker Solutions on Equinor’s Mariner oil platform were the latest to threaten strike action over pay, Britain’s largest workers union said on Friday.

A series of strikes loom over the North Sea this summer.

Workers on some of Total’s North Sea fields are due to start a series of 24-hour and 12-hour strikes on Monday.

Another set of workers are also considering strike action.

Unite said it will ballot 2,500 offshore oil services workers after rejecting a pay increase offer from the Offshore Contractors Association (OCA). This could affect 106 platforms, it said.

The Aker strike would involve about 200 workers and would likely take place between early August and early October.

Mariner is a heavy oilfield located some 150 km (93 miles) east of the Shetland Islands that is due to start production in the second half of 2018 with a target plateau output of 55,000 barrels per day.

Its operator, Equinor, formerly known as Statoil, was not immediately available for comment.

Strike action by 1,600 Norwegian rig drillers ended on Thursday after starting on July 10.