Norway’s $1tn Government Pension Fund, the world’s second-largest institutional investor, has sold out of a US energy group controlled by Warren Buffett’s Berkshire Hathaway, in its latest round of environmental and ethical divestments.

The giant investor said it would drop its bond holdings in PacifiCorp, a power utility that serves several states in western US, under its policy of selling out of firms that have more than 30% of their business in thermal coal.