Southern Water has apologised to hundreds of its customers after sending their personal details out in a mass email.
The names and addresses of 200 customers were included in an email sent to 400 people taking part in a free water butt offer run in conjunction with Portsmouth City Council.
The error – blamed on an IT glitch by the company’s contractor – has prompted fears that householders could be left vulnerable to rogue callers posing as installers working for Southern Water.
A Southern Water spokeswoman said: ‘This email came from the contractor which is carrying out the water butt installations on behalf of Southern Water and Portsmouth City Council.
‘The error has been attributed to an IT problem. We are in discussion with the contractor to work out exactly how it happened and to ensure it does not happen again. We would like to apologise to all those affected.’
In February this year, the company issued a public apology after it was fined £20.3m by regulator Ofwat for poor service and misreporting performance data.
The average annual water bill in the Southern Water area is £359, compared to a national average of £330.
Earlier this month, water companies in England and Wales announced proposals to increase bills by up to 25% between 2010 and 2015. The regulator, Ofwat, will decide how much companies will be permitted to raise prices in November 2009.
Installing a water meter could save some households £66 a year on their bills.