Shares in advertising agency WPP (LON:WPP) fell over 5 percent on Monday, after its chief executive announced his resignation over financial misconduct allegations.

The company, which is the world’s largest advertising group, announced that Sir Martin Sorrell had chosen to leave his post in a statement released on Saturday.

The announcement came just over a week after the allegations of misconduct surfaced.

Despite the claims, WPP maintained that the alleged misconduct ‘did not involve amounts that are material’ after conducting an independent investigation.

Sir Sorrell commented on his decision to depart the firm:

“Obviously I am sad to leave WPP after 33 years. It has been a passion, focus and source of energy for so long. However, I believe it is in the best interests of the business if I step down now.”

Whilst Sorrell will not receive pay out or pension, he may be set to make around £19 million over the course of the next five years from his WPP shares.

Sorrell is the longest-serving FTSE 100 chief executive, having overseen WPP’s meteoric rise to become the largest advertising firm in the world.

Group’s chairman Roberto Quarta said Sorrell had been the driving force behind WPP’s expansion and thanked him for his “commitment to the business over more than three decades”.

Sorrell was one of the highest paid bosses in the country, with his £70 million renumeration package in 2016 making headlines as the largest in UK corporate history.

As of currently, shares in the company are trading -5.35 per cent in the wake of the announcement (12.55GMT).