Campaigners have been sharing photos of themselves posting empty crisp (chip) packets to the company to highlight the issue but Royal Mail has now asked them to stop.
The protest began with 38 Degrees, who want consumers to post the hashtag #PacketInWalkers in support of the petition, which started last year thanks to Geraint Ashcroft, 61, from Wales.
The grandad is calling on PepsiCo, which owns Walkers Crisps, to create a recyclable or non-plastic and compostable alternative to its current packets and has so far received more than 300,000 signatures in support for his petition.
But now, Royal Mail has asked campaigners to stop posting the crisp packets in letter boxes because if packets are not placed in envelopes they need to be sorted by hand.
"We strongly encourage customers not to post anything into the postal system which is not properly packaged,” a Royal Mail spokesperson said.
"Crisp packets can't go through the machines, they are not normal mail items therefore my hardworking colleagues need to manually sort them, which adds to time."
In response to the campaign, Walkers Crisps said in a statement it has received some returned packets and recognizes the efforts being made to bring the issue of packaging waste to its attention.
“The returned packets will be used in our research, as we work towards our commitment of improving the recyclability of our packaging,” a Walkers spokesman said.
Despite not being able to confirm if consumers will see any changes before 2025, the company highlighted its current sustainability efforts, claiming ‘PepsiCo has committed to achieving 100% recyclable, compostable or biodegradable packaging by 2025’ and it is carrying out some compostable packaging pilots in the US, India and Chile.
It said in May last year it joined the New Plastics Economy initiative led by the Ellen MacArthur Foundation; in April 2018, PepsiCo UK joined the UK Plastics Pact, led by WRAP; and it is working with biotechnology leader, Danimer Scientific, on the development of biodegradable flexible packaging.
It is estimated Walkers Crisps makes around 11 million packets of crisps in the UK every day.
“There’s huge public concern about the amount of plastic being produced, and that means it’s crunch time for Walkers to decide if they will listen to their customers,” said Cathy Warren, 38 Degrees campaigner.