Prince Charles is funding his charities with profits from shipping royal-branded mineral water 6,000 miles to the Middle East in an arrangement that has been described by Friends of the Earth as "completely insane".

The prince campaigns vociferously for reductions in greenhouse gas emissions and recently attacked the global food industry over the problems caused "when we ship vast quantities of commodities halfway round the world". But he has used the proceeds from the export of bottles of Duchy Originals water from a Scottish estate close to Balmoral to luxury supermarkets in the Gulf to fund his favoured charities. It is part of a sales drive for the prince's groceries brand in conjunction with Waitrose which has delivered £10m in profits over the past three years.

Luxury Duchy Originals hampers, including bottles of lemon and ginger drinks, are also on sale at the SuperNature grocery 10,000 miles away by sea in Singapore, while bottles of Duchy-branded organic ale made with barley from the prince's Home Farm at Highgrove are being offered by drinks retailers in Australia and New Zealand.

Environmentalists have called for the prince to bring the trade to an immediate halt. "Shipping bottles of water around the world is completely insane," said Craig Bennett, director of policy and campaigns at Friends of the Earth.

"It is absolutely ludicrous when there is perfectly good drinking water in the Middle East. It is very hard to dress up shipping water thousands of miles as helping the environment."

The story has emerged 52 months after Charles made an apocalyptic speech in Rio de Janeiro warning that the world had "less than 100 months to alter our behaviour before we risk catastrophic climate change".

The Royal Deeside water is shipped from Aberdeenshire to branches of Spinneys in Dubai, Bahrain and Abu Dhabi. Waitrose declined to say how much goes to the Gulf because of "commercial sensitivity" but said it was "very small". One thousand cases sent via the Suez canal would produce an estimated 1.5 tonnes of carbon dioxide.

Jeanette Longfield, co-ordinator of Sustain, a campaign for sustainable food policies, said shipping water was "lunacy". "Once this is drawn to Prince Charles's attention I would hope he will decide this is not a good idea," she said.

Prince Charles has cast himself as a protector of the environment. Duchy Originals, set up by the prince in 1990 "to promote organic food and farming and to help protect and sustain the countryside and wildlife", began exporting in earnest after signing the Waitrose deal. It publishes a charter that explains: "We aim for the smallest environmental footprint."

The Prince of Wales's Charitable Foundation last year gave £200,000 to the Soil Association, which campaigns to "minimise the local and global ecological footprint" of food.

A spokesman for the prince said: "The Prince of Wales is aware that Waitrose is committed to reducing its environmental impact wherever possible. Duchy Originals from Waitrose has so far donated around £3m a year to the Prince's Charitable Foundation, a grant-giving charity, and to the Prince's Countryside Fund, which supports Britain's hard pressed rural communities."

The majority of royalties are generated from the sale of Duchy products in UK supermarkets but profits of around £45,000 came from exports, including some that are air-freighted.

A spokeswoman for Waitrose said: "We are committed to reducing our environmental impact. The vast majority of products we export are sea-freighted, with less than 1% of our Duchy Originals from Waitrose exports air-freighted, which makes sense from an environmental and a commercial perspective." Waitrose said it did not directly supply Duchy Originals hampers to Singapore or Duchy beer to the Middle East.

It is not the first time Charles has been accused over his carbon footprint. In 2009 he was criticised for hiring a private jet to tour Europe promoting climate change issues.