Consumers have an average of 17 plastic bags stored at home while more than half support retailers charging for them, according to a Which? survey.

The poll by the watchdog found 56 per cent of consumers in England and Scotland support a 5p charge for bags but, among those opposed to a charge, 70 per cent think they already pay enough for their shopping and 45 per cent think they should be entitled to free bags.

A charge is already in place in Wales while Northern Ireland is introducing one next year.

The survey also revealed that half of shoppers who have used an online supermarket in the last 12 months felt too many bags were used.

Supermarkets provided nearly 800 million more single-use plastic carrier bags last year than they did two years ago, according to figures from Waste Resources Action Plan (Wrap).

The 10 per cent increase pushes the number of bags supplied to shoppers to eight billion, or 120 per customer, just for supermarkets.

Although 8 per cent of people surveyed by the consumer group confessed to throwing away bags in the general waste after their initial use, 92 per cent said they do reuse bags either for shopping (53 per cent) or as bin liners (74 per cent).

While supermarkets provide bag recycling bins, 62 per cent of consumers think they do not do enough to encourage customers to use them.

Leading supermarkets signed an agreement in 2008 to supply 50 per cent fewer single-use plastic bags by 2009. They achieved 48 per cent but plastic bag use has risen again since the agreement ended in May 2009.

Marks & Spencer is the only one of the seven supermarkets to charge for bags, resulting in a 78 per cent drop in bag use at its stores.

Which? executive director Richard Lloyd said: “Plastic bag use is on the increase again with 10 per cent more being given away. That's 800 million extra bags leaving supermarkets since 2010.

”Customers should reuse bags wherever possible and take advantage of recycling points in stores where they're available. We'd also like to see recycled material used for new plastic bags as much as possible.“

A Defra spokesman said: ”We want to work with retailers to help them lift their game to cut the number of bags they hand out.

“We are monitoring the results of the charging scheme in Wales and the outcome of the Scottish consultation on a charge.”

:: Which? polled 1,116 adults between May 30 and June 1.