British Prime Minister Theresa May was accused by opponents of failing to stand up to the United States over its withdrawal from the Paris climate accord.
May's office says she spoke to President Donald Trump after his announcement and "expressed her disappointment with the decision."
But Britain did not sign a joint statement by the leaders of Germany, France and Italy, who said they regretted Trump's decision and insisted that the accord cannot be renegotiated.
May's office would not say whether she had been asked to sign it. May noted that Japan and Canada - fellow members of the G7 group of nations - also were not signatories, but like Britain remain committed to the Paris agreement.
"It's an important international agreement on climate change," May said.
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"I made the UK's position clear to President Trump last week at the G7 meeting, as did the other G7 leaders, and I made the position clear to President Trump last night."
Trump's announcement sent the issue of climate change - and May's attempts to bolster the trans-Atlantic "special relationship" with the US - to the top of the agenda Friday in campaigning for Britain's June 8 election.
Labour Party leader Jeremy Corbyn accused May of "subservience" to Trump.
Liberal Democrat leader Tim Farron urged May to use whatever influence she has to urge Trump to reverse his decision.
"You have gone to Washington to hold Donald Trump's hand, now is the time to hold his feet to the fire," Farron said.
Scottish First Minister Nicola Sturgeon said not signing the declaration was an "appalling abdication of leadership."
