'Bags-for-life' face 5p charge in Wales
The 5p charge on single use carrier bags in Wales could be extended to heavy-duty so-called "bags-for-life".
Welsh government ministers are considering removing the exemption on the heavier bags.
The single-use bag charge was introduced two-years ago, cutting use of the bags in Wales by 90%.
Ministers say there is a risk that the heavier bags are now being treated as "throw-away", even though retailers charge between 5p and 10p for them.
In their proposals for the environment bill, the government says ministers should have powers to impose a minimum charge on bags-for-life if they believe the sale and disposal of them continues to rise.
Recent data has shown the sale of bags-for-life by supermarkets in Wales has more than doubled between 2010 and 2012.
In terms of weight, this corresponds to around 30% of the reduction in weight of the thin-gauge single-use bags.
In their white paper on the bill, the government says: "An increase in demand for bags-for-life was expected in Wales following the introduction of the charge as consumers got used to reusing their bags and purchased enough bags-for-life for their shopping needs.
"However, there is a potential risk that many consumers start treating a low-cost reusable plastic bag as a 'throw-away bag' and discard it prematurely.
"This 'substitution effect' is likely to have significant adverse environmental impacts if these types of bags are disposed of inappropriately; as such bags are typically made of heavier gauge materials and take longer to degrade."
The government has also stated that it will not prevent retailers donating the 5p levy to any good cause, not just the environmental charities that were originally envisaged.
It said: "From the information provided by the 246 retailers that have signed up to the code on the Welsh government website and from the retailers' records we have seen, many of the good causes that are currently benefitting from the net proceeds are, for example, cancer charities and children's hospices amongst others.
"The Welsh government's stated policy aim in relation to the charge is that it would prefer that environmental good causes benefit from the charge.
"However, the Welsh government does not wish to cut across the existing relationships that retailers have with other good causes that contribute to the economic, social and environmental wellbeing of Wales."
The proposals in the bill come ahead of a review of the current bag charging policy, which will take place next year.
First Minister Carwyn Jones has said that review will also examine the practices of some retailers.
He said: "There is a policy review, which will be undertaken after November of next year, but, certainly, at this moment in time, there are no plans to change the levy.
"It depends, of course, on what that review shows and on what we see as the practices of some supermarkets at the moment, which are charging just 1p more for bags for life, thus, avoiding, in some ways, the levy.
"We will have to keep a close eye on that, of course."