Four major UK investors said on Sunday they supported Rockefeller family shareholders who are lobbying for the separation of the chairman and chief executive positions at ExxonMobil, the world’s biggest non-state-owned oil company.

The investors – F&C Asset Management , Co-operative Insurance Society , Morley Fund Management, part of Aviva, and the West Midlands Pension Fund – said they would vote to separate the duties now carried out by Rex Tillerson at the company’s annual meeting on May 28.