WPP chief Martin Sorrell has backed Nick Clegg's surprise call for a tax on the wealthy, but criticised the coalition for failing to get the economy back on track.

Sorrell - who confirmed yesterday that the advertising giant is to relocate its HQ to London in an attempt to lower it's own tax bill after a self-imposed ban saw it take up business residence in the lower tax jurisdiction of Ireland - said of Clegg's proposed tax that he 'wouldn't be against it.'

Launching into more scathing remark's of the government's management of the economy, he said, 'The government's troubles started with the Budget. One of the Budget provisions was to move the income tax marginal rate down from 50pc to 45pc. From an entrepreneurial view it didn't make sense. If you want to improve entrepreneurial activity, reduce the rate of capital gains tax. Don't mess about with income tax.

'The government could have said, "We will reduce the marginal rate of tax to 45pc or 40pc over the life of the parliament" if they wanted to keep the right wing of the Conservative Party happy. The government has shot itself in the foot. They did reduce it and I didn't see the need to do it at that point in time,' said Sorrell.

His sharp comments alongside WPP's announcement of pre-tax profits of £358m, a 7% rise from £334.3m for the six months to June 30, dragged down by more sluggish US revenues.