Sarah Bentley, chief executive of Thames Water, has resigned effective immediately.

Alastair Cochran, chief financial officer, and Cathryn Ross, director of strategy and regulatory affairs, will jointly assume the role of interim chief executive.

Bentley joined Thames in 2020 and quickly adopted a no nonsense approach to tackling underperforming parts of the business in an eight-year turnaround plan.

Cochran and Ross were both brought onboard by Bentley as part of the restructuring of the senior team.

Bentley turned down a performance-related bonus this year and admitted the company was not where she wanted it to be in terms of progress for the first two years of her plan.

Bentley said: “It has been an honour to take on such a significant challenge, and a privilege to serve Thames Water’s dedicated and inspirational colleagues. The foundations of the turnaround that we have laid position the company for future success to improve service for customers and environmental performance. I wish everyone involved in the turnaround the very best.”

She will continue to support the interim chief executives to ensure a smooth transition while the board begins the recruitment process for a replacement.

Chair Ian Marchant said: “I want to thank Sarah for everything she has done since joining the company in 2020, building a first class executive team and leading the first phase of the turnaround of the Company. On behalf of everyone at Thames, the board wishes her every success for the future.”