People should see their water bills drop by an average of £34 by 2015.

Ofwat, the water regulator, has published its final decisions on the prices water and sewerage companies can charge customers, which will see the average bill drop by £3 a year or £34 by 2015.

Ofwat said that as a result of its decision, more than £22 billion will be invested in maintaining and improving services to consumers, yet still keeping customer’s bills broadly flat until 2015.

It said that more than £935 will be invested for every property across England and Wales.

Regina Finn, Ofwat Chief Executive Officer, said: “People can shop around for the best deal on many things, but not water. Our job is to do this for them.

“Customers have told us that they want us to keep water and sewerage charges flat while maintaining a safe, reliable supply of water. That’s what we’ve delivered.

“It doesn’t end here. We will now make sure the companies deliver on their promises. If they don’t we’ll take action to protect customers.”

However the water watchdog, the Consumer Council for Water, remains concerned about the impact on some customers who may inadvertently receive higher bills. Customers’ bills will vary depending on where they live, and the watchdog says they range from a drop of 7% to an increase of 13% before inflation.

It says the announcement by Ofwat was “unrealistic” in July, when it suggested that bills would fall by £14, which received plaudits by customers.

Dame Yve Buckland, Chair of the watchdog, said: “The overall deal will be acceptable to many customers who told us that they wanted bills to remain flat, and over England and Wales, average bills are actually going down by one per cent.

“However, we would give the deal a seven out of ten because Ofwat has eased off the companies, meaning that some customers will face higher bills.”

Water companies still have the opportunity to appeal Ofwat’s decision should they disagree.