Prominent environmental group Friends of the Earth Action is urging voters to support Hillary Clinton instead of Green Party candidate Jill Stein.

The liberal DC-based organization, which endorsed Bernie Sanders over Clinton during the Democratic primary and ran ads on his behalf, argued in an op-ed published Tuesday that Stein and her party “are not credible standard barriers for the progressive movement or Sen. Sanders’ Revolution.”

“In endorsing Sen. Sanders, Friends of the Earth Action was supporting someone who inspired and rallied new people to our democracy and could accomplish change as president” wrote Friends of the Earth Action president Erich Pica. “In Hillary Clinton, while we disagree with many of her positions, we see someone who will be very capable running the government. In Dr. Stein, we see someone who shares our values on important issues, but has absolutely no track record.”

The group acknowledged its past criticisms of Clinton -- including her slowness to oppose the Keystone XL pipeline, her onetime praise of the Trans-Pacific Partnership and her “ties to fossil fuel lobbyists” -– but argued that Stein has been largely absent on important progressive fights as well.

“Where was she during the battle against the Keystone XL pipeline, the Keep It In The Ground movement, the Fast Track Trade Promotion Authority battles, the fight for a $15 dollar minimum wage, same-sex marriage and all the other major progressive gains over the past several years?” Pica wrote.

“They did not take part. The Green Party is a political organization in name only, though we wish it were much more.”

The full op-ed has been posted on Medium.com here.