Yorkshire Water has announced its chief executive is stepping down - a day after the company was given the lowest environmental rating by regulators.
Nicola Shaw said there "remains a huge amount of work to do", but the business was on a "stronger footing for delivery across all aspects of its work".
"This now feels like the right time to begin an orderly transition to the company's next chapter," she added.
The Environment Agency (EA) said on Thursday that it had downgraded Yorkshire Water's environmental rating from two stars out of four - to one.
The EA found that the water supplier, which serves more than five million people in the Yorkshire region, had 335 pollution incidents in 2025. It was fined £1.2m in total last year.
The rating means Yorkshire Water has been classed as poorly performing - alongside Southern Water, Thames Water and South West Water.
The grade also automatically blocks the water supplier from giving out bonuses to bosses under new rules introduced last year.
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Yorkshire Water previously came under scrutiny for payments to Ms Shaw worth £1.3m between 2023 and 2025 which were made through the Jersey-incorporated company Kelda Holdings.
The firm stressed at the time the payments were made by shareholders rather than billpayers.
Ms Shaw, who has led the business for four-and-a-half years, will leave her post on 1 January.
She will be replaced by Nicola Medalova, a former National Grid executive, who will join the firm next week as chief executive-designate for a "structured handover", Yorkshire Water said.
Ms Medalova said the company was facing "huge challenges" and pledged to have a "relentless focus" on delivering "for customers, communities and the environment".
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