Prices are 10% higher north of the border
Water customers in Scotland have been getting a raw deal, according to the country's industry watchdog.
Alan Sutherland told BBC Scotland that people north of the border were getting "considerably less" for their money than those in the south.
And the water commissioner forecast that bills would continue to rise unless Scottish Water met its efficiency targets.
The unitary body took over from the country's three former water boards last year.
Scottish Water's own figures have also shown that households north of the border pay 10% more than those in England and Wales.
There have also been widely-publicised concerns about water quality in Scotland.
On Tuesday, the BBC's Frontline Scotland programme will reveal the commissioner's findings that Scotland rates badly for customer service.
The three former water authorities were surveyed in 2001/2002 on the handling of complaints, general billing inquiries and general contact with the public.
The reason they are paying too much for their water is because of the inefficiencies in the running costs and the capital costs
All three were ranked below every company south of the border.
Mr Sutherland said: "What the research has shown is that Scottish customers are getting considerably less for their more expensive charges than customers in England and Wales.
"We are getting worse water quality and we are getting worse levels of customer service."
He said water charges would rise over the next two years and would continue to go up unless Scottish Water met its efficiency targets.
"Customers are paying too much for their water," he said.
"The reason they are paying too much for their water is because of the inefficiencies in the running costs and the capital costs.
Scottish Water isn't as effective as it should be because we have only had one year
Scottish Water chairman
"By 2006, if Scottish water achieves its efficiency targets, then the prospect for prices is quite good."
Scottish Water's chairman, Alan Alexander, said he was confident that those targets would be met.
He said prices were going up because two thirds of Scotland's water pipes needed to be renewed at a cost of £2bn.
He pointed out that there were 8,000 burst pipes in Scotland every year.
"Scottish Water isn't as effective as it should be because we have only had one year," he added.
"We are working to a four-year regulatory framework and we have said perfectly clearly that we will achieve the targets that have been set for us over that period."
The Frontline Scotland programme, Trouble at the Tap, will be broadcast on BBC One Scotland at 2235 BST on 13 May.