An investigation has been launched against WPP founder and CEO Sir Martin Sorrell following an allegation of “personal misconduct”.

A terse statement to the stock exchange states that independent counsel has been appointed by WPP’s board to investigate the allegation against Sir Martin.

“The investigation is ongoing. The allegations do not involve amounts which are material to WPP,” the statement concludes.

Reports refer to a statement issued by Sir Martin, in which he rejects the allegation “unreservedly”, but recognised that it must be investigated. He will not play a part in managing the investigation.

“As a significant share owner, my commitment to the company, which I founded over 30 years ago, remains absolute—to our people, our clients, our shareholders and all of our many stakeholders,” he said.

Its share price currently stands at 1.124p (Thursday 4 April), having rallied from 1.095p on Wednesday.

Sir Martin is one of the UK’s most well-known and senior executives. He launched the advertising business in 1985 through the acquisition of wire baskets business Wire and Plastics Products plc. The business was renamed and refocused as WPP in the following two years, with a number of UK and US marketing services acquisitions.

While his proclamations on the condition of the advertising market are intensely followed and covered, in recent years he has been in the public eye for his huge remuneration: in 2016 he picked up £48m, down from 2015’s £70.4m. The 2015 pay deal was opposed by one-third of its shareholders.

There has also been discussion among investors about succession planning at WPP.