Karen Blackett, UK country manager at WPP, is to replace Tom George as UK chief executive of Group M.

The new role, which will see her lead strategy and operations for Group M’s agency brands which include Mindshare, MediaCom, Wavemaker, Essence and M/SIX, is in addition to her current responsibilities.

The move comes a week after WPP’s shares fell to their lowest level since 2012 after the company announced that net sales had sunk by 1.6% to £13.2bn in 2019.

Group M was singled out as a poor performer, having lost global media accounts including HSBC and American Express at the end of 2018.

Blackett originally joined MediaCom in 1999 and became chief operations officer for EMEA in 2008 and UK CEO three years later.

She received an OBE in 2014 and became chairwoman of MediaCom UK and Ireland in 2016.

She said her priorities for Group M were helping the media agencies “accelerate and fly” and greater collaboration with other parts of WPP.

George joined WPP from Zenith in 2005 as managing director of MEC UK (now known as Wavemaker) and became CEO two years later.

He said: “Now feels like the right time to move on and in Karen we have a fantastic leader taking over the reins.

“I’ve had the privilege of working with Karen during my time in the group and she will undoubtedly drive further growth for the Group M and WPP business.”