The UK’s two largest supermarket chains have committed to end the sale of cotton buds with plastic stems, which are the most common litter from toilets flushed on to the country’s beaches.

Both Tesco and Sainsbury’s will replace the plastic stick with paper by the end of 2017 in their own-brand products.

Other major companies, including Morrisons, Asda and Boots, are currently considering a plastic ban, while Waitrose, the Co-operative and Johnson & Johnson have already committed to paper stems. The moves follow a growing campaign that now has 130,000 backers.

The tide is turning against plastic pollution in the oceans, which is known to harm marine life when they confuse it for food. People eating seafood can also ingest the plastic and, earlier in November, the chief medical officer for England announced she would conduct an investigation into the impact on human health.

Plastic bags found on UK beaches by the Marine Conservation Society’s annual beach clean fell by more than half in 2016, after a 5p charge was levied on the bags by the government. Ministers have also said they will ban plastic microbeads in toiletries, which also wash into the oceans. There are estimated to be 5tn pieces of plastic floating in the world’s seas.

Natalie Fee, founder of the City to Sea campaign to cut plastic pollution, said: “We’re delighted with the announcements to ‘switch the stick’ from plastic to paper stem buds. Whilst they still shouldn’t be flushed, this move will stop millions of plastic stems ending up in the marine environment each year and is a huge win in the fight against marine plastic pollution.”

A spokesman for Sainsbury’s said: “We have been working hard to improve this product. Our new cotton buds, with 100% biodegradable stems, will be available before the end of 2017.” A Tesco’s spokesman said: “We’re committed to ensuring all of our own label cotton bud products will be made with paper stems, and will do this by the end of 2017.”

“These are great commitments from Tesco and Sainsbury’s, but we’d like to see much more prominent ‘don’t flush’ labelling on cotton bud sticks,” said Emma Cunningham at the Marine Conservation Society. “We found over 23 [plastic] cotton bud sticks on every 100m of beaches we cleaned in September. The message is clear: only pee, poo and paper should go down the loo.”

The City to Sea campaign is run with 38 Degrees, whose Trish Murray said: “The public’s overwhelming support for this campaign shows that there is a real desire for retailers to provide environmentally sound alternatives.”