LONDON (AP) — Britain says it plans to ban the sale of new petrol and diesel cars by 2035 in a bid to speed up its efforts to tackle climate change.

But the U.K. government's commitment to reducing greenhouse gas emissions has been 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.

The U.K. said Tuesday that it would bring in a ban on fossil-fuel cars and vans even earlier than 2035 “if a faster transition is feasible.” The ban will also include hybrid vehicles.

The announcement was timed to coincide with the launch of Britain's plans for the climate summit, known as the 26th Conference of the Parties, or COP26. It is scheduled to be held in Glasgow in November.

Johnson was kicking off a year of buildup Tuesday alongside naturalist David Attenborough and Italian Prime Minister Giuseppe Conte. Italy is hosting a preparatory meeting for the conference.

“Hosting COP26 is an important opportunity for the U.K. and nations across the globe to step up in the fight against climate change,” Johnson said in remarks released in advance by his office. “As we set out our plans to hit our ambitious 2050 net zero target across this year, so we shall urge others to join us in pledging net zero emissions.”

Britain has pledged to eliminate its net greenhouse gas emissions by 2050. But the government’s advisory Committee on Climate Change has warned that domestic action to slash carbon dioxide and other gases that contribute to global warming is lagging far behind what is needed.

Britain’s tenure at the helm of COP26 is getting off to a rocky start. On Friday, Johnson sacked Claire O’Neill, a former British government minister appointed last year to head up the event. Her replacement has not been announced.

O’Neill strongly criticized the prime minister in a letter to the Financial Times, saying Britain’s efforts to fight climate change were “miles off track.”

“When you asked me to be your COP President … you promised to ‘lead from the front’ and asked me what was needed: ‘money, people, just tell us!’” she wrote. “Sadly, these promises and offers are not close to being met.

"The Cabinet sub-committee on climate that you promised to chair, and which I was to attend, has not met once," O'Neill added.

“You had a vision for Brexit and you got Brexit done. As I write, we have less than 7,000 hours before the start of COP26, where we have a chance to set a new global vision for climate recovery and build a new consensus for global climate action. Please get this done too.”