British lawmakers have written to Prime Minister Theresa May, urging her to challenge US President Donald Trump on his views on climate change when the two leaders meet on Friday.

Trump has dismissed climate change as a "hoax" and vowed during his presidential campaign to pull the United States out of the 2015 Paris Agreement designed to curb greenhouse gas emissions blamed for global warming.

"As one of the world's largest emitters ... his approach to reducing emissions could determine whether we, in the UK and people round the world, experience or avoid the worst impacts of climate change," the letter from the cross-party Environmental Audit Committee said.

May is set to be the first foreign leader to meet the new US President on Friday, with the talks expected to focus on trade. Environmental Audit Committee chair Mary Creagh said that May should use the opportunity to demonstrate Britain's commitment to fighting climate change.

"The Prime Minister has said she won't be afraid to challenge the new President. So she should start by telling him climate change is not 'a hoax'," Creagh said.

Scientists warn that rising global temperatures must be stalled to stave off the worst effects of climate change, including floods, droughts and rising sea levels.