Sir Keir Starmer has insisted he “stands” with Denmark after Donald Trump dramatically threatened to annex Greenland.
The prime minister also said that his Danish counterpart Mette Frederiksen was “right” to refuse the US president any claim to the territory.
It comes in the wake of President Trump repeating his territorial claims over Greenland following his decision to capture Venezuela’s president Nicolas Maduro.
Sir Keir’s signal of solidarity with Nato ally Denmark comes as the US president suggested over the weekend that Venezuela may not be the last country subject to American intervention, after his administration struck Caracas. He has also previously made territorial claims against another Nato ally, Canada.
“We do need Greenland, absolutely,” Mr Trump told the Atlantic magazine, following the operation in Venezuela.
President Trump has been making territorial claims on Greenland since January last year and in February Sir Keir gave Denmark his support in opposing the US demands.
Meanwhile Katie Miller, the wife of one of Mr Trump’s senior aides Stephen Miller, posted a picture on social media of Greenland in the colours of the American flag alongside the word “soon” following the Venezuela operation.
The Danish leader hit back, writing in a statement that “the US has no right to annex any of the three nations in the Danish kingdom”, of which Greenland is one.
Asked during a visit to a community centre in Berkshire about Ms Frederiksen’s strong language, Sir Keir told Sky News: “Well, I stand with her, and she’s right about the future of Greenland.”
While it is understood that Sir Keir has not spoken to Trump yet, the UK’s position has been outlined by foreign secretary Yvette Cooper in a call to US secretary of state Marco Rubio which took place on Sunday evening.
The prime minister’s official spokesperson also did not refute reports in The Times that the UK plans to abstain from a UN security council resolution condemning US actions in Venezuela.
Elsewhere, the prime minister was asked by the BBC if he agreed with calls from the Danes for the US president to stop proposing American annexation of the island.
“Yes,” Sir Keir replied, adding: “Greenland and the Kingdom of Denmark are to decide the future of Greenland, and only Greenland and the Kingdom of Denmark.
“Denmark is a close ally in Europe, it is a Nato ally, and it’s very important the future of Greenland is, as I say, for the Kingdom of Denmark, and for Greenland, and only for Greenland and the Kingdom of Denmark.”
The Labour government has in recent months been forging closer ties with Denmark, and has been taking cues from Ms Frederiksen’s government – which is of a similar political tradition – on how to crack down on illegal migration.
Former attorney general Dominic Grieve argued that there was “no legal basis” for the Venezuela action and warned that the renewed claims on Greenland showed that Trump was working off “fantasies about the United States right to intervene anywhere within the western hemisphere.”
“One can see how he thinks I could get away with seizing Greenland,” Mr Grieve told The Independent.
“We’re living with a completely maverick and amoral US president who is a serious and significant danger to world peace.”
Former head of the UK Supreme Court Lord Sumption also said that the Venezuela action was illegal.
He told The Independent: “The attack on Venezuela was plainly illegal. The contrary position is not seriously arguable.”
However, the prime minister maintained his refusal to condemn President Trump over the US action against Venezuela despite growing unease from Labour MPs and opposition parties including the Greens and Lib Dems.
Labour’s former shadow attorney general Dame Emily Thornberry became the most senior Labour figure to denounce the US actions, piling pressure on Sir Keir to disown Mr Trump’s conduct and stating “it must be called out”.
Dame Emily, chair of the commons foreign affairs select committee, warned: “You can’t walk into a smaller country and take its resources, tell its leadership what to do or throw the leaders in jail.
“There are rules. These came out of the chaos, suffering and bloodshed of the Second World War.
“Might must not be right. Just because larger countries can walk into smaller ones doesn’t mean they are allowed to.”
But speaking to reporters, the prime minister said: “What’s happened here in Venezuela is obviously really important. We have long championed a peaceful transition to democracy, because the president was illegitimate.”
Sir Keir also said international law needed to be the “anchor” for the future of Venezuela after the US removed president Maduro at the weekend. He added that the US will “want to justify” its actions in international law.
But the PM would not be drawn on whether he believed the US had breached international law when asked directly.
He told reporters: “International law is really important. It’s the framework, and it’s for the US to set out its justifications for the actions that it’s taken. But it is a complicated situation. It remains a complicated situation. The most important thing is stability and that peaceful transition to democracy.”
The PM added: “I think the vast majority of Labour MPs would say that they want to see democracy in Venezuela. That is hugely important.”