Sir Keir Starmer did not raise the issue of the Falkland Islands' sovereignty with Donald Trump during a 10-minute phone call yesterday, GB News understands.
Last week, a leaked Pentagon email set out measures to "punish" Nato allies, including the UK, after Britain withheld the use of British airbases in the Iran war.
The fate of the archipelago, which was first landed on by English explorers some 120 years before Argentina existed as an independent state, has since been called into question.
However, on the most recent phone call between the world leaders, Downing Street said the pair only discussed the Washington shooting, which took place on Saturday night.
TRENDING
Stories
Videos
Your Say
A Downing Street spokesman said: "The Prime Minister spoke to President Trump this afternoon.
"He extended his best wishes to the President and First Lady following the shocking scenes at last night’s White House Correspondents’ Dinner.
"He expressed his relief that the President and First Lady were safe and wished a speedy recovery to the officer injured."
With no mention of the Falklands debacle, critics have urged the Prime Minister to do more to protect Britain's national security.
Downing Street said the pair only discussed the Washington shooting which took place on Saturday night
| GETTYShadow Foreign Secretary Dame Priti Patel told GB News that "allies and adversaries alike can see Starmer’s feebleness and this is what they are looking to exploit".
"Britain needs a leader, not a lawyer, who has failed to ask basic questions about our national security and who is putting Britain’s standing in the world in jeopardy," the MP added.
Since the leaked Pentagon email, Donald Trump has been slammed for "lashing out" at the UK after it emerged that the US could drop diplomatic support for the Falklands.
The memo suggested Washington could reassess its backing for what it termed British "imperial possessions", including the Falklands.
LATEST DEVELOPMENTS:
Argentina has continued to claim sovereignty over the territory after the Falklands War in 1982.
Its President, Javier Milei, has reasserted the country's claim to the territory and called for direct negotiations with Britain.
The country has been upgrading its military capabilities with US assistance, with Mr Milei aligning himself with many of Mr Trump's foreign policy positions.
On Friday, he wrote on social media: "The Malvinas [Falklands] were, are, and will always be Argentine. Long live freedom, damn it!"
A Government spokesman has insisted that Falklands sovereignty rests with the UK and that self-determination remains paramount | GETTYThe US historically has remained neutral to the challenge of Falklands sovereignty.
US officials have not confirmed the existence of the memo, but a spokesman suggested Mr Trump had "credible options" to address allies who were "a paper tiger".
Since the opening salvos of the conflict, President Trump has rowed with Keir Starmer over the UK’s initial reticence to allow American warplanes to use British bases.
Limited authorisation was eventually given for facilities such as RAF Fairford in Gloucestershire and Diego Garcia to support defensive missions targeting Iranian missile installations threatening the Strait of Hormuz, though only after Iran began retaliatory strikes.
Last month, GB News revealed Britain was woefully underprepared to defend the Falkland Islands, with veterans of the 1982 conflict warning the UK lacked "credibility" as a global power.
A Government spokesman insisted sovereignty rests with the UK, and self-determination remains paramount.
Foreign Secretary Yvette Cooper added the Government's commitment to the Falkland Islands was "unwavering".