The boss of Thames Water has stepped down with immediate effect weeks after being forced to give up her bonus over the company’s environmental performance.

The company said that Sarah Bentley would leave the board on Tuesday, but will continue to support her interim replacement until a new full-time boss can be found.

Ms Bentley, who was appointed in 2020, said in May that she would give up her bonus after the company’s environmental and customer performance suffered.

But even after giving up the bonus, the chief executive managed to double her pay, raking in £1.5 million.

At the time Gary Carter, a national officer at the GMB union, said that Ms Bentley’s plan to give up the bonus was “nothing more than a flimsy PR stunt”.

Because she declined it, the company never said how large the 51-year-old’s bonus would have been, but the year before her performance-related pay had reached £496,000.

Chief finance officer Alastair Cochran, who will now take over as interim co-chief executive, also gave up his bonus at the time.

He will now run Thames Water together with Cathryn Ross, the former Ofwat chief executive who joined the business in 2021.

On Tuesday chairman 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.”

Ms 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.”

Liberal Democrat environment spokesperson Tim Farron said: “This has to be a watershed moment for the scandal-ridden company.

“Thames Water is a complete mess and it’s time ministers stepped in to reform the firm from top to bottom.

“The days of profit before the environment must end.”