Warren Buffett made his first move to capitalise on the latest round of credit market turbulence by agreeing to pay $4.7bn for Constellation Energy Group, a US power company whose shares have been hammered over a feared 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, tentatively agreed yesterday to buy Constellation for $26.50 a share – less than half the company's market value a week ago.

Constellation started scrambling on Tuesday to find a buyer or secure an emergency capital infusion, when it became apparent that its investors were losing confidence in the stability of its commodities trading operations and credit ratings.