Sustain found that only the Environment Department (DEFRA), the Food Standards Agency and the Department for Transport had introduced a policy of offering tap water.
Those using bottled water include the Cabinet Office, the Treasury, the Department of Health and the Department for Education and Skills, as well as the House of Commons.
The survey coincides with the publication of a report on the bottled water industry. 1 The report finds the bottled water market is growing at 6-7% per year despite the product costing "around 500 times as much as tap water".
Sustain says the packaging waste generated and energy used to transport water is a concern. Some brands on sale in the UK originate from Canada, Turkey and Fiji.
The Environment Agency said it also uses only tap water.