"Rejecting fossil fuel influence is a smart move for the Biden-Harris campaign," Charlie Jiang, climate campaigner with Greenpeace USA, said in a statement Thursday. "Voters are hungry to elect a climate champion. Joe Biden is running on the most ambitious climate platform in history, but it won't mean much if his transition team is stacked with oil and gas insiders."

In a document titled "Biden-Harris Transition Team Ethics Plan," the campaign states that "in addition to instituting a robust code of ethical conduct, Vice President Biden aims to ensure that those who serve are aligned with his values and policy priorities, and have not, for example, been leaders at fossil fuel or private prison companies."

But the ethics plan falls well short of adhering to a list of demands issued last month by a coalition of nearly 150 climate organizations, which urged Biden to "ban all fossil fuel executives, lobbyists, and representatives from any advisory or official position on your campaign, transition team, cabinet, and administration" if elected president.

While the Biden campaign will require transition team members to sign a pledge promising to disqualify themselves from "involvement in any particular Biden-Harris transition team matter" if they have "engaged in regulated lobbying activities with respect to such matter" within the previous 12 months, the requirement comes with a substantial loophole.

"Persons who have registered as federal lobbyists within the last 12 months may only serve as transition team members with advance approval of the General Counsel," the document states, suggesting that lobbyists for the fossil fuel industry could ultimately be permitted to serve on the transition team.

Jiang said that while the Biden campaign's ethics plan "is a strong start," it "is not the end of the road."

"We urge Biden to commit to banning all fossil fuel executives and lobbyists from his cabinet and administration," Jiang added. "Personnel is policy, and we need experts in the White House who put climate and environmental justice ahead of corporate profits."

On Twitter, Collin Rees, senior campaigner at Oil Change U.S., called Biden's move "a key first step" made possible by constant pressure from grassroots climate activists.

"Committing to a fossil-free transition team is exactly what we need to see heading into a new administration with climate impacts mounting rapidly," Rees added in a statement Thursday. "Keeping fossil fuel representatives out of the federal government is a position that's extremely popular with Democrats and the entire American public, and builds on the key improvements Biden has made to his climate plan since the primary. The Biden-Harris campaign is clearly listening to its potential allies, and this willingness to listen and adapt will be critical in the months ahead."