Barclays is seeking to raise as much as £4bn ($8bn) from outside investors as it seeks to shore up its balance sheet without having to launch a rights issue that could lead to aggressive writedowns.

The UK bank is working on a plan to offer stakes to large investors, including several sovereign wealth funds, in which shares would be purchased at a premium to current prices. Existing shareholders would be given the opportunity to participate in the offering on similar terms although terms that dilute their holdings by 5 per cent or more will require their approval.