Richard Buxton, the renowned fund manager, has accused Edward Bramson of “scaremongering” following the US-based activist investor’s warning that Barclays will have to raise fresh capital unless the bank shrinks its trading operations.

The comments from Buxton, a long-standing shareholder in Barclays, come in response to a letter sent last week by Bramson, who has built a 5.5% stake in the bank through his company Sherborne Investors, which claimed the UK lender would need to scale back its investment bank.