Bank of America’s $4.1bn offer for Countrywide Financial was thrown into doubt on Thursday when a large shareholder in the biggest US mortgage lender said it would vote against the deal.

SRM Global Fund, a Monaco-based hedge fund which has a 5 per cent stake, said the offer “considerably undervalued” Countrywide. It also plans to ask the Securities and Exchange Commission to investigate changes in Countrywide’s share price ahead of last month’s offer.