Thames Water has had a trading dispute with Castle Water regarding incorrect meter readings upheld by the Trade Disputes Committee (TDC).

Thames stated that approximately 12,000 supply point identifications (SPIDS), used to identify a new retailer to switch retail services, had the data item yearly volume estimate (YVE) changed to a value of “one” in the central market operating systems (CMOS) by Castle Water – causing an impact on its wholesale revenue and leakage reports.

Following the TDC’s decision at the meeting held last month, Castle Water and Thames Water agreed to the rectification plan as set out by the committee.

However in a letter sent out to customers last week, Castle Water accused Thames Water of using inaccurate meter information to back-bill its customers.

It claims Thames has proposed to charge all customers without an accurate meter reading history based on volume estimates unrelated to their own usage.

It is understood that the Olympic Park in east London has been billed using estimates for leisure facilities based on original bills during the much greater footfall of the 2012 games.

It is thought that multiple NHS sites, University College London, the universities of Surrey, Kingston, the South Bank and St Mary’s and 50 schools will be affected as a result of the dispute, with one school with an annual bill of £10,000 understood to be facing back-billing of £70,000.

In a letter written to customers Castle Water’s chief executive, John Reynolds, said the company wanted to make them aware of a “major potential change” to their bills which “could multiply them by up to seven times”.

The letter specified that Thames Water has proposed to charge all customers based on “volume estimates unrelated to their own usage”, a move which Castle describes as “unjustified”.

Thames Water has since responded by accusing Castle of giving out “inaccurate and misleading” information and accused the non-domestic supplier of using “scare tactics”.

It added it remained a matter for Castle Water as to what it charged its customers and said the business retailer had “underestimated” some customers’ volume of water usage.

A Thames Water spokesperson said: “This letter to customers is very concerning as it is inaccurate and misleading on several counts.

“We have not changed our tariffs and what Castle Water charges its customers remains a matter for them.

“The position is that some retail customers’ volume of water usage has been underestimated by Castle Water and this has resulted in underpayment for water consumption.

“We agree meters are the fairest way to pay and welcome the fact that Castle Water is now actively seeking meter readings, including the commonly followed practice of asking for these from customers.

“However, we’re surprised that such a large retailer is using such scare tactics with its customers and has misunderstood the rules which underpin the industry.”

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