Britain's Royal Mail is asking residents to stop mailing empty potato chip packets back to the manufacturer as an environmental protest.

Royal Mail officials said the campaign, backed by activist group 38 Degrees, is causing delays for workers at postal facilities because the empty Walkers chip bags have 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 representative told Sky News. "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."

People have been mailing their empty chip bags back to Walkers in recent weeks to protest the company's packaging, which takes 75-80 years to decompose.

The company announced during the summer that it was aiming to make the packaging recyclable by 2025, but protesters say the goal isn't fast enough.

Social media users have posted photos of themselves mailing empty Walkers packets back to the company with the hashtag "#PacketInWalkers." A petition circulated by 38 Degrees calling on Walkers to move up the timetable of the packaging plans has garnered over 5,000 signatures.

Jarred Livesey, an environmentalist who has mailed several empty backs back to Walkers, said he plans to continue the protest while still abiding by Royal Mail's request.

"I will continue to return packs to Walkers -- I'll just use a recycled envelope," he told ITV News.