Warren Buffett has made his first move in response to the latest round of credit market turbulence by agreeing to buy $4.7bn Constellation Energy Group, a US power company whose shares have been hammered over fears of a lack of liquidity in its commodities trading business.

MidAmerican Energy, a holding company of energy assets that is majority-owned by Mr Buffett’s Berkshire Hathaway, agreed on Thursday to buy Constellation for $26.50 a share – at less than half the company’s market value a week ago.