WPP is investigating an allegation of personal misconduct against its CEO Sir Martin Sorrell.

The world’s biggest advertising organization said its board had selected autonomous insight to lead the investigation.

“The allegations do not involve amounts which are material to WPP,” a statement issued on Tuesday night said.

The claims about Sir Martin, 73, were first reported on Tuesday by the Wall Street Journal.

The Journal likewise revealed that WPP’s board was looking at whether Sir Martin abused company resources, referring to anonymous sources.

That issue was not tended to in the organization’s announcement, which just affirmed an examination concerning the personal misconduct allegation.

One of the UK’s best-known business pioneers, Sir Martin has built WPP into a firm that overwhelms the advertising business and has around 134,000 staff in more than of 100 nations.

He has been CEO of the organization for over three decades.

A month ago, WPP cautioned that 2017 was “not a pretty year” for the firm because of flat growth, regardless of benefits of more than £2 billion.

The share price has declined sharply over the past 12 months from £17.31 to close at £11.17 in London on Tuesday.