Britain's largest crisps maker needs to act now on plastic packet waste, says the man behind a petition campaign.
It has led to a packaging protest which has seen people posting empty bags back to Walkers Crisps using its freepost address.
The Royal Mail urged people to use envelopes as posting packets was clogging sorting offices.
Geraint Ashcroft, from Pontypridd, said the company needed to bring forward plans to abandon current packets.
More than 300,000 people have signed his petition on the campaign site 38 Degrees calling on Walkers and other snack manufacturers to switch to environmentally-friendly packaging.
But Mr Ashcroft said the current packets cannot be recycled and are a blight on land and sea.
"It takes so long for them to degrade, there are packets being picked up on beaches that are 30 or 40 years old," said Mr Ashcroft.
"The situation isn't getting any better. There's going to be 28 billion produced between now and when Walkers and KP etc. think they'll have a solution, which is in 2025.
"That'll be another 28 billion going into landfill and ultimately our seas. That is an enormous amount."
The 38 Degrees online network got behind his campaign and urged the public to respond by posting empty packets back to the crisp maker and "flood Walkers social media with pictures of us popping them in the post".
The Royal Mail is legally obliged to deliver the crisp bags, but they need sorting by hand.
Sorting office managers urged the public "not to post anything into the postal system which is not properly packaged".
38 Degrees said it would update "the thousands of Walkers's customers who are taking part" in its campaign about the Royal Mail request.
But campaigner Cathy Warren added: "Walkers produce a staggering 7,000 plastic crisp packets a minute which they don't pay a penny to clean up. They need to listen to their customers and take action now."
Mr Ashcroft said the move to send back empty packets was "not my decision", and he wanted to concentrate on getting Walkers to implement changes.
"Recycling isn't enough. It won't sort the ones already on the beaches," he said.
"We need biodegradable, we need compostable bags."
Walkers met Mr Ashcroft to discuss the issue in August.
The Leicester-based firm has pledged to make all its packaging 100% recyclable, compostable or biodegradable by 2025 and is piloting compostable packaging in the US, India and Chile.