The energy regulator is considering whether Scottish Power is unfairly locking customers on a popular fixed rate deal that ended last month into an expensive capped tariff.
The Prime Minister has called on current account providers and the regulator to urgently "negotiate" to prevent payout delays if bank charges are ruled unfair.
The Treasury Select Committee has launched an inquiry into the fact lenders encourage the public to needlessly apply for credit that could make future borrowing harder and more expensive.