LONDON (Reuters Life!) - British restaurants are pushing customers into buying expensive bottled water instead of offering them tap water for free, the government's consumer watchdog said on Friday.

A five-star hotel in London charges water at 50 pounds ($102) a litre and even chain restaurants charge 3.80 pounds for bottled mineral water.

But despite the high prices, one in five diners are "too scared to ask" for tap water, a survey of just under 1,000 people carried out on behalf of the National Consumer Council (NCC) found.

Nine out of every 10 restaurants are pushing consumers to buy bottled water and fail to offer them free tap water, the survey found.

"Some restaurants are willing to offer tap water to their customers but the majority push water just to make a quick profit," said Carl Belgrove, senior policy advocate at the NCC.

Seventy percent of respondents said they felt bottled water was too expensive in restaurants and want to see free tap water readily available.

Britons consume 37.6 litres of bottled water per person a year.

More than 90 percent of bottled water comes in plastic bottles. Their disposal and the impact on climate change through the shipping of millions of bottles around the world has raised concern among environmentalists.