New York (CNN Business) Coca-Cola and PepsiCo, two major sellers of plastic bottles, have made sweeping sustainability commitments . Now they are stepping away from a plastics lobbying group .

Both soft drink companies are trying to increase the amount of recycled plastic they use in bottles. They want to improve recycling infrastructure and ensure their packages are recyclable.

But the Plastics Industry Association has ties to the American Progressive Bag Alliance, which encourages states to make plastic bans illegal. Participation in the association could tarnish Coca-Cola and Pepsi's images as companies working to find solutions to plastic pollution.

The association took positions that "were not fully consistent with our commitments and goals," Coca-Cola said in a statement last week, noting that it withdrew from the group earlier this year. Pepsi said it had joined the association to learn about innovation as it works to "achieve a circular economy for plastics."

"We do not participate in the policy advocacy work of the association or its subsidiaries, and our membership will conclude at the end of this year," Pepsi said.

Coke and Pepsi "made the wrong choice" by being a part of the lobbying organization, said Dianna Cohen, CEO of the nonprofit Plastic Pollution Coalition. The optics of membership, she added, "are really bad."

Plastic pollution is a major problem.

Cutting ties with the Plastic Industry Association is a sign that "companies understand that they cannot publicly say they want to end plastic pollution, while financially supporting an association that lobbies for our continued reliance on throwaway plastics," said Greenpeace USA Oceans Campaign Director John Hocevar in a statement.

The move may help reassure some customers. But as people grow more worried about the negative impacts of plastic pollution on the environment as well as on animal and human health, companies like Pepsi and Coke will have to go even further to find a solution.

Tackling plastic pollution

Both companies are trying to figure out ways to reduce their use of virgin plastics and increase recycling. They're also exploring alternatives to plastics, like aluminum, that are easier to recycle.

PepsiCo announced recently that its Aquafina-brand water will be sold in aluminum cans at US fast food and restaurant chains as soon as next year. The company is testing out a broader rollout to retail stores.

"Tackling plastic waste is one of my top priorities and I take this challenge personally," PepsiCo CEO Ramon Laguarta said at the time. "We are doing our part to address the issue head on by reducing, recycling and reinventing our packaging." Pepsi has committed to using only recyclable, compostable or biodegradable packaging by 2025, and it's pledged to make new plastic bottles using 25% recycled material.

Plus, Coca-Cola last year launched a World Without Waste initiative that encompasses its recycling goals , which include collecting and recycling the equivalent of every bottle or can it sells by 2030. The company has also committed to making its bottles and cans out of at least 50% recycled material in the next 11 years.

The companies are also exploring refill stations that eliminate single-use packaging altogether.

Pepsi is selling a high-tech water cooler that lets customers fill up their own bottles with flavored or unflavored, still or carbonated water in varying temperatures. Coca-Cola has launched a similar product for Dasani on college campuses.

Leaving the lobby

Those initiatives made membership in the plastics trade group problematic, at least from a PR standpoint. The Plastics Industry Association is not only a lobbying group. Some of its initiatives, like helping recycling, may overlap with those of Coke and Pepsi.

"Our members work together to align their efforts to put recycling and sustainability at the forefront of their businesses," said Patty Long, interim president and CEO of the Plastics Industry Association, in a statement.

The plastics association says it does not itself lobby for legislation that bans plastic or hold an official position on those laws. It says that it operate separately from the bag alliance and has different memberships and dues.

But a page on the association's website redirects to the bag alliance site, and the contact email for the bag alliance has the same suffix as the association's. An association representative declined to share how the groups are connected.

Activists started pressuring Coke, Pepsi, and other companies to leave the plastic association last year.

The shareholder activist group As You Sow and Walden Asset Management called attention last year to corporate involvement with the Plastic Industry Association, and wrote letters to the CEOs of Coca-Cola and PepsiCo, among others.

This year, Greenpeace also drew a line between the Plastic Industry Association and anti-plastic ban laws.

The plastics association said Greenpeace is responsible for companies' withdrawal from the group.

"We are aware that several prominent brands that are members of the association have been targeted by a persistent Greenpeace activist campaign to pressure them to leave our association," Long said, calling the efforts "unfortunate."

— Update: This article has been updated to clarify the Plastic Industry Association's lobbying activities.