An internal email seen by the Guardian instructed staff to "be conscientious about avoiding any terminology misaligned with the administration's priorities". Employees were told the restrictions applied to all staff, regardless of whether they worked directly in communications.

The EERE is the government's main funder of renewable and low-carbon technologies. Critics inside the agency said the move represents a continuation of President Donald Trump's rollback of green policies, which has included major cuts to renewable energy programmes.

One employee, speaking anonymously, said: "Banning the use of these words would silence key elements of DOE's mission. What's worse is that the secretary is freezing or cancelling research into solar, wind and other clean energy technologies."

Among the prohibited terms are "energy transition", "clean or dirty energy", "carbon footprint" and even references to "tax credits" and "subsidies" associated with Biden-era support for renewables. The list is part of a broader set of restrictions across government agencies, with around 200 terms reportedly flagged by the Trump administration this year.

The DOE press secretary denied that any such directive had been issued, saying there was "no ban" on language related to climate science and insisting the administration "remains committed to transparency and open dialogue".

But Secretary Wright, who leads the department, has openly railed against climate policy. At last week's UN General Assembly, he claimed climate action raised energy costs and "reduced life opportunities". He also defended a widely criticised DOE climate report accused of spreading misinformation and confirmed the cancellation of $13bn in funding for renewable projects.

The developments follow Trump's broader effort to erase references to climate change from federal agencies since returning to office in January. At the UN, the president went further, calling the climate crisis "the greatest con job ever perpetrated upon the world."