One of Britain’s top businessmen is being investigated by his company over alleged misconduct.

WPP, the advertising and public relations multinational, has confirmed its chief executive, Sir Martin Sorrell, is under investigation.

In a short statement, the company said it had appointed “independent counsel to conduct an investigation in response to an allegation of personal misconduct” against Sir Martin.

It added: “The allegations do not involve amounts which are material to WPP.”

In a statement reported by the BBC, Sir Martin, who is Jewish, said media reports had stated that WPP “is investigating an allegation of financial impropriety by me, specifically as to the use of company funds.

“This allegation is being investigated by a law firm. I reject the allegation unreservedly but recognise that the company has to investigate it.”

He said he understood the investigation would be completed shortly.

Over three decades Sir Martin turned WPP from a manufacturer of wire baskets to a global player in marketing which incorporated leading companies such as J Walter Thompson, Ogilvy and Mather and Burson and Marsteller.

Knighted for his services to business in 2000,he has been one of the country’s highest paid executives with a package worth over £40 million last year.

In an interview with the JC two years ago, he said he had “no thoughts of retirement” at the age of 71. “Age is meaningless, it's all about how you feel,” he said. “ I couldn't imagine not coming in to work on a regular basis.