The Welsh Assembly government is urging retailers to give the income they receive from charging customers for carrier bags to good causes.
The Single Use Carrier Bags Charge (Wales) Regulations 2010, which will come into force in Wales in October, say that a retailer "must charge a minimum of 5 pence for every single-use carrier bag supplied new".
A spokeswoman for the Welsh government said it estimated this could raise between £2m and £3m for good causes in the first year.
There is no legislation in place to force shops to give the money to charities, but separate guidance about the legislation says: "We can’t tell you what to do with the money, but we want it to be passed on to good causes in Wales, particularly environmental projects."
The spokeswoman said the government had asked shops to give the proceeds to good causes on a voluntary basis, but if they did not comply it would consider introducing further legislation that would force them to do so.
The legislation will compel retailers to keep a record of the number of bags they issue and account for how proceeds from the sale of bags are used.
Asked whether similar legislation could be introduced in England, Lord Henley, the recycling minister, said retailers had to take responsibility for cutting down on the number of single-use carrier bags they handed out.
"If results do not improve, we will consider additional measures to make this happen, including legislation," he said in a statement.
A spokeswoman for the Department for Environment, Food and Rural Affairs said it was too early to tell whether this would include measures to force proceeds to be given to charities.
Chloe Stables, parliamentary and media manager at the National Council for Voluntary Organisations, welcomed the legislation in Wales.
"We would encourage the Westminster government to roll it out across the country," she said. "It could provide a much-needed injection of cash for charities and would reduce plastic bag use."