The move would allow the Welsh government to move ahead with its Deposit Return Scheme (DRS) by permitting the inclusion of glass.
The schemes in England, Northern Ireland and Scotland are not set to include glass.
Westminster’s hesitation in approving an exclusion to the act was partly blamed for the eventual delay of the Scottish DRS.
Owen Derbyshire, Chief Executive of Keep Wales Tidy, one of the signatories of the letter, said: “People across Wales care deeply about the quality of their local environment.
“A Deposit Return Scheme that includes glass would make a real difference to litter levels, public safety and the condition of our public spaces.
“Wales has taken a thoughtful, evidence-based approach to developing this policy, and it’s important that we are able to move forward as planned.”
The letter, which is addressed to the secretaries of state of Defra, Business and Trade, and Wales, highlights Wales’s “long-standing leadership” in environmental policy.
It notes that the plastic carrier bag charge was first introduced in Wales and later adopted more widely across the UK.
The letter argues that allowing Wales to proceed with glass in its scheme will allow the continuation of such devolved decision-making and leadership.
The organisations warned that preventing Wales from implementing its scheme would “raise wider questions about the ability of devolved governments to plan and legislate with confidence in areas that are clearly devolved”.
The campaigners also claimed that glass was originally included in plans for the UK-wide scheme, and that later changed at a UK level, which led to the current divergence.
The open letter is signed by Afonydd Cymru, Cardiff Rivers Groups, Keep Wales Tidy, Marine Conservation Society, Surfers Against Sewage, Trash Free Trails and Wales Environment Link. It can be viewed in full here.
The Welsh Deposit Return Scheme (DRS)
The DRS in Wales is proposed to include plastic bottles, cans and glass.
It is set to go live in October 2027, at the same time as those in England, Northern Ireland and Scotland.
In the open letter, the charities identify that the materials targeted by the DRS are found in over half of public spaces.
Data from the Marine Conservation Society showed that glass can be found on 49% of all Welsh beaches.
