Shoppers in Wales may have to start paying for plastic bags before May 2011.

The compulsory charge for single-use bags is expected to be between 5p and 15p, although this is yet to be decided.

The British Retail Consortium has slammed the move, saying that “the best way to achieve lasting change is to educate customers, not penalise them”.

The Welsh Assembly Environment minister Jane Davidson said she would seek agreements with large retailers to give the proceeds to environmental causes.

Wales is the first country in the UK to start charging for one-trip carrier bags, exploiting powers provided under the Climate Change Act.

Yesterday the Welsh Assembly revealed the charge will be introduced before the next Assembly election.

BRC business environment director Tom Ironside said: “Education and encouragement, rather than compulsion, is the best way to achieve lasting customer change. For some reason bags have been seized on as a symbol of our use of resources, despite their relatively low environmental impact.

“By introducing a bag charge, Wales becomes the first country in the UK to impose extra charges on shoppers at a time when they’re already feeling the pinch. This will especially hit low-income families.