Ofwat, a Britain's water regulator, has written to United Utilities, Thames Water and Bristol Water urging the companies to reduce water prices.The regulator's concerns, announced on Wednesday, were focused on United Utilities' wholesale wastewater price control, Bristol Water's wholesale water price control and the proposed separate price control for Thames's costs relating to the Thames Tideway Tunnel.Ofwat said in each case the companies' bid is one-fifth higher than their recommended model.The watchdog said the warning would allow time for the water companies to reconsider their plans.Bristol Water said in a statement: "We appreciate the feedback from Ofwat and we will be seeking clarity on the wholesale cost assessment which Ofwat has carried out, in order to consider what additional information we can provide to the regulator and what changes we need to make to our business plan."JF