The information about the thirsty work of governing was obtained by Green Party TD Ciaran Cuffe, who this weekend described the water expenditure as a "luxury". He said: "We're spending the best part of 1m on bottled water when for the most part Irish tap water is eminently drinkable. It seems like an extravagance to me."

The figures show a big variation on bottled water expenditure across government departments. The Department of the Taoiseach spent almost 6,000 last year on 18 water coolers in Government Buildings. The department also purchased 700 250ml bottles of De Bream mineral water ( 313.27) and 2,000 bottles of a similar size of Nash's mineral water ( 891.04). Cuffe was told that these purchases were used for "conferences, functions, seminars and official meetings".

At the defence department, 1,172 litres of bottled water were bought in 2005 at a cost of 1,600. "The amount of tap water used is unquantifiable, " the department told Cuffe.

Along with bottled water payments, most departments pay charges to local authorities for the supply of water. The communications department paid 4,800 to Dublin city council, which also received 9,069 from the department of enterprise, 8,000 from health and 5,885 from the Taoiseach's department.

The Department of the Environment paid almost 42,000 to bottled water suppliers and local authorities in 2005. There was a more frugal attitude in Finance, with water costs of almost 24,000 last year which included 3,838 litres of bottled water. The total bill at the Department of Foreign Affairs came to almost 43,000, of which 8,926 was for mineral water at the Passport Office in Dublin and 242 for the Passport Office in Cork.

The biggest annual cost for mineral water and local authority charges was at offices under the responsibility of agriculture minister Mary Coughlan, which paid out 200,000 in the last 12 months.