Britain announced Tuesday that it plans to ban the sale of new petrol and diesel cars by 2035 — five years earlier than its previous target — in a bid to speed up efforts to tackle climate change.

But the U.K. government’s commitment to reducing greenhouse gas emissions was questioned by the woman who was appointed by Prime Minister Boris Johnson to head a United Nations’ global climate summit — and then was fired last week.

Sacked conference president Claire O’Neill said Britain’s efforts to fight climate change were “miles off track.”