Ross-based organisation the Marine Conservation Society welcomed the proposal from the National Assembly of Wales that shoppers could be charged 20p for plastic carrier bags at shop checkouts.

The Sustainability Committee says the fee would raise about £13 million a year for environmental causes and cut litter by encouraging people to keep reusable bags.

The committee rejected calls for an outright ban because it would be too difficult to enforce, especially along the border with England if Wales went it alone, committee chairman Mick Bates said.

Marks & Spencer began charging customers 5p for carrier bags this year and WH?Smiths in Ross charges 6p to discourage use. When the Reverend Derek Bedford was Mayor of Ross he campaigned to reduce the numbers of plastic bags used by shoppers in the town.

MCS is one of the organisations which contributed to the committee during the six months of evidence gathering. MCS highlighted the impacts of plastic bags to marine wildlife. Plastic bags can be mistaken for food and consumed by a wide range of marine species, including several endangered species such as marine turtles. Plastic has been recorded as a cause of entanglement in many marine animals.

Decreasing plastic bag use is supported by the Welsh public and the MCS have been working with several towns in Wales to help them become plastic bag free including Abergavenny.

Gill Bell, Welsh Officer, said, "Plastic bags are potentially lethal to wildlife and MCS are thrilled that the committee is supporting a national levy on plastic bags at check outs. Imagine every time you reuse your plastic bag alternative, you could potentially be saving marine wildlife, such as whales, dolphins or turtles".

A similar levy in Ireland resulted in a 90% decrease in plastic bag use. MCS surveys have shown an increase in the number of plastic bags on UK beaches. Data from Beachwatch 2007 (the annual UK wide beach clean and survey organised by the MCS), showed 7,504 plastic bags were found on 354 beaches around the UK. On average 44 bags were found for every kilometre of coastline surveyed. Plastic bags ranked number 15 in the top 20 most common litter items recorded, accounting for 2% of all beach litter.

Mick Bates AM, Chair of the Assembly Sustainability Committee, said: "We do not consider that banning plastic bags in Wales would be a feasible option for the Welsh Assembly Government.

"The committee believes that a levy is the best and most practical form of intervention that the Welsh Assembly Government could make and that profits raised from such a levy should be used for environmental benefits.

"Consumers in Wales will soon see that a small change in their purchasing and disposal behaviours can quickly affect a large change on the environment."

Welsh Ministers will have the powers to impose a levy under a new clause in the Climate Change Bill which is expected to finish its passage through Parliament in November.

An estimated 648 million plastic bags per distributed in Wales each year. Almost all of these are distributed free of charge, although using figures calculated by Keep Wales Tidy, the hidden cost to Welsh consumers of these bags is more than £6 million a year. It is estimated that a plastic bag takes between 450 and 1,000 years to degrade.

At a levy of 10p per bag, the annual revenue from a levy would be £6.48 million, a levy of 15p per bag would raise £9.72 million and a levy of 20p per bag, £13.96 million.