Whitmey will take on the newly created role at Tesco, leading its Clubcard loyalty scheme, next year.

She became CEO of Havas Helia – Havas’ data and digital business – in 2011 when it rebranded Evans Hunt Scott (EHS). Tesco was one of EHS’s original clients when it set up in 1995.

In a statement, Chris Hirst, chairman of Havas UK and chief executive, Europe, said: "When the opportunity arose to lead the UK’s original loyalty scheme, we couldn’t stand in Tash’s way. While we are hugely disappointed to see her leave, it’s a brilliant opportunity for her and we’re equally excited to have her as a client."

Whitmey said: "It’s a real wrench to leave helia, but I depart in the knowledge that the agency is in great shape, and has an exciting future. The opportunity to work on Clubcard at Tesco was too exciting to miss, and I can’t wait to get started. I look forward to the continuation of helia and Tesco’s longstanding and successful relationship…albeit from the other side."