Barclays rebuked rival bankers and short-selling hedge fund managers yesterday for suggesting that its numbers could not be believed as it reported a 33 per cent slide in first-half pre-tax profits to an “acutely disappointing” £2.8 billion.

The bank wrote off another £2.4 billion in bad loans and other credit impairment charges.

Bob Diamond, the Barclays president, conceded there had been suggestions that the bank was not accounting conservatively enough. He said: “Clearly, there has been some noise in that area from people with vested interests in making it appear that way.”

Mr Diamond argued that Barclays had successfully offloaded £6 billion of assets at prices at or close to their value in the books, giving the lie to critics who said that it had overvalued problem assets. “There's no better proof than that,” he said.

Barclays also defended its unusual policy of ignoring falls in the market prices of leveraged loans. Barclays argues that because it plans to hold its £5 billion of buyout loans to maturity and the borrowers are meeting all interest payments, there is no need for a markdown.

John Varley, the chief executive, said that the numbers had been scrutinised by the board and the auditors. “You've got to be consistent. We've not shifted our accounting policy,” he said. “I don't accept the view that people don't believe our writedown figures. We've given a considerable level of disclosure today.”

Share traders largely welcomed the figures as "resilient" in the face of such difficult market conditions, marking the shares 6p higher to 375p, 25 per cent above the 282p at which Barclays raised most of its £4.5 billion in fresh equity capital last month.

However, several analysts maintained that the writedowns might not be enough and continued to question the robustness of the accounting.

Bruno Paulson, a senior AllianceBernstein analyst, said: “There is welcome new disclosure, but questions will remain about the adequacy of some of the marks [asset valuations], notably on the monoline exposures.”

Barclays lifted its provision against monolines, which insure bondholders against default, to £433 million, but analysts said that it was still much less conservative than other banks.

Mr Varley apologised for the collapse in the Barclays share price and said that it would take a long time to regain the business volumes enjoyed before the credit crunch hit.

Although the overall figures were in line with City expectations, Barclays revealed that it had suffered £103 million of losses as a result of the failure of hedge fund clients.

Barclaycard, the credit card division, put in the best performance with a 30 per cent increase in profit to £388 million.

The interim dividend was held at 11.5p, payable in cash.

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