Water regulator Ofwat said it was planning to fine Severn Trent Water £35.8 million for deliberately providing false information to the regulator and providing poor service to its customers.
The fine represents 3 per cent of Severn Trent's annual turnover.
Ofwat said it was imposing a £34.7 million fine for deliberately misreporting some key customer service information. The company also incurred a fine of £1.1 million for providing sub-standard services to customers in 2005-06 by failing to meet Guaranteed Standards of Service.
Ofwat said that the cost of the fine would be carried entirely by Severn Trent shareholders and could not be passed onto customers.
Regina Finn, Ofwat chief executive, said, Severn Trent Water's behaviour was unacceptable. The size of the proposed fine reflects how seriously Ofwat takes the deliberate misreporting of information.
This sends a clear message to the company and to the rest of the water sector - Ofwat will protect consumers and companies must comply with their legal obligations or pay the price. Any further attempts to deliberately mislead Ofwat could lead to even bigger fines in the future.
Ofwat regulates water and sewerage providers in England and Wales