The regional chairman representing Severn Trent Water's customers is urging the firm to ensure they do not suffer as a result of a criminal investigation into the company.
Severn Trent Water is being investigated by Ofwat, the water watchdog, and the Serious Fraud Office (SFO), following concerns about the reliability of information supplied by the water company between 2000 and 2003.
Information submitted to Ofwat shapes the cost of bills, levels of service and funding for future projects provided by Severn Trent.
A senior member of Severn Trent Water's staff alleged that discrepancies were uncovered in the company's data on leakage accounts.
Concerns about Severn Trent's data were first raised by Daniel Donnelly, the firm's Income and Debt Reporting Manager, which led to a four month inquiry by PricewaterhouseCoopers before the matter was then passed to Ofwat.
Sir James Perowne, Chairman of the Consumer Council for Water Midlands (CCWater), said: "These are very serious allegations and the SFO must complete its investigation before we know the scale of the impact on consumers.
" Ofwat has assured CCWater that consumers will be compensated if it were found that customers have been overcharged as a result of the alleged mis-reporting."
Severn Trent maintains that customers have not been overcharged as a result of the alleged error although it has assured Ofwat that it will pay customers compensation if this is later found to be untrue.