Some of the largest institutional shareholders in Abbey National have urged the Competition Commission not to block counter-bids for the bank from UK rivals. Abbey has currently agreed a takeover deal with Santander Central Hispano, Spain's largest bank, for around £8bn.

UK fund management houses, Legal & General and Isis Asset Management, argue that the UK banking sector is already hugely competitive and excluding a UK bid against the current Santander deal may not offer the best value for shareholders.