The long-serving chairman of Thames Water is heading for the exit in the wake of a series of failures that have provoked an extraordinary attack on the company by industry watchdogs.

The Telegraph understands that long-serving chairman Peter Mason will this week announce his departure from the board after a string of fines for repeated water and sewage leaks in recent years.

He is expected to step down next March after twelve years at the helm of the board.

Thames Water, which supplies water services to 15 million homes, is under major pressure to improve its performance after Ofwat chairman Jonson Cox made an an unprecedented call for the company to review its board structure and overhaul its approach to executive and shareholder payouts.

The company has faced claims it has underinvested in maintenance and repairs in favour of generous dividends for its owners.