Britain's most senior civil servant has complained that Downing Street is finding it “unbelievably difficult” to make arrangements with the United States for the crucial G20 summit.

Sir Gus O'Donnell, the Cabinet Secretary, reportedly said that the handover to the Obama Administration was hindering discussions about the meeting in London next month.

The Prime Minister hopes that the summit on April 2 will produce a co-ordinated global strategy to tackle the economic downturn.

So far, his attempts to get his Washington and European allies to agree to a coherent common platform for the meeting have proved frustrating.

The G20 nations, which represent about 90 per cent of world economic activity, include not only the traditional G7 members but the European Union and emerging economic powers such as China and Brazil.

Mr O'Donnell said that No 10 was having trouble even getting in touch with key personnel at the US Treasury department. “There is nobody there,” he told a civil service conference in Gateshead. “You cannot believe how difficult it is.”

His comments come after Downing Street was left frustrated by the White House’s chaotic handling of Gordon Brown’s visit last week. No 10 aides were left scrambling when the President's staff changed press arrangements at the 11th hour.

Sir Gus's remarks appear to confirm the problems Mr Obama has faced in getting his administration staffed and up to speed during the worst economic crisis in decades.

The Times reported last week that Tim Geithner, the Treasury Secretary, had been forced to operate virtually on his own without any of the 17 deputies his department is supposed to have.

Sir Gus criticised the US system of new administrations appointing their own senior civil servants as “absolute madness”.

The Whitehall & Westminster World website, whose publisher, Dods, organised yesterday's event in Gateshead, reported that Sir Gus had emphasised the importance of continuity for projects such as the Olympics.

“You get to a certain point, and you can’t go any further,” Sir Gus said. “If there’s a change of administration, you’re out, and a whole new bunch of people come in who probably haven’t been in government before.”

Preparations for the summit are due to step up a gear this weekend when G20 finance ministers, including Alistair Darling, the Chancellor, and Mr Geithner, join central bankers at a luxury hotel in West Sussex that Winston Churchill used as a weekend retreat.

The main summit will be held at the ExCeL centre in the Docklands, where Mr Brown will receive heads of government from the EU and 19 other leading economies, including Mr Obama on his first visit to Europe as President.

Even though Mr Obama is visiting Britain for the G20, he is expected to meet the Queen at Buckingham Palace.

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