In a phone conversation this afternoon, Sir Keir Starmer conveyed a strong message to Donald Trump, asserting that imposing tariffs on allies for their commitment to NATO’s collective security is misguided, according to a statement from Downing Street.

This dialogue follows President Trump’s announcement that he intends to impose a 10% tariff on all goods imported from the UK to the United States starting February 1, with plans to increase this rate to 25% by June 1. These tariffs are purportedly linked to Trump’s controversial proposal for the U.S. to acquire Greenland from Denmark.

Trump indicated that this tariff policy would similarly affect several other European nations, including Denmark, Norway, Sweden, France, Germany, the Netherlands, and Finland.

On a busy Sunday afternoon, Sir Keir engaged in multiple discussions, among them a significant call with the U.S. President, as confirmed by No. 10.

In addition to Trump, Starmer reached out to Danish Prime Minister Mette Frederiksen, European Commission President Ursula von der Leyen, and NATO Chief Mark Rutte to discuss the implications of the U.S. tariff strategy and its impact on international alliances.

A Downing Street spokeswoman said: ‘In all his calls, the Prime Minister reiterated his position on Greenland.

‘He said that security in the High North is a priority for all Nato allies in order to protect Euro-Atlantic interests.

‘He also said that applying tariffs on allies for pursuing the collective security of Nato allies is wrong.’

The Prime Minister joined European allies warning of a ‘dangerous downward spiral’ in Nato today after the US President threatened a trade war over Greenland.

A joint statement from Denmark, Finland, France, Germany, the Netherlands, Norway, Sweden and the UK said they stood ‘firmly behind’ the ‘principles of sovereignty and territorial integrity’.

The President has shocked the military alliance by warning that opponents of an American takeover of the Danish territory will be hit with punitive tariffs from February 1.

In a bombshell post on his social media site, Mr Trump said levies will start at 10 per cent – and potentially rise to 25 per cent if they have not capitulated by June. 

Mr Trump also appeared to take issue with a Danish-led military exercise conducted with allies in Greenland this week, saying the countries had ‘journeyed to Greenland, for purposes unknown’.

The UK sent a single military officer for the Arctic endurance exercise.

In a joint response this afternoon, the European powers stressed that the exercise was preplanned – and reiterated their solidarity to Denmark and Greenland. 

They said: ‘As members of Nato, we are committed to strengthening Arctic security as a shared transatlantic interest. The pre-coordinated Danish exercise Arctic Endurance conducted with Allies, responds to this necessity. It poses no threat to anyone.

‘We stand in full solidarity with the Kingdom of Denmark and the people of Greenland. Building on the process begun last week, we stand ready to engage in a dialogue based on the principles of sovereignty and territorial integrity that we stand firmly behind.

‘Tariff threats undermine transatlantic relations and risk a dangerous downward spiral. We will continue to stand united and coordinated in our response. We are committed to upholding our sovereignty.’

Meanwhile Danish PM Mette Frederiksen described Trump’s threats over Greenland threats as ‘fundamentally unacceptable’, Danish newspaper Berlinske reported. 

‘It is fundamentally unacceptable to threaten a good ally like Denmark,’ she told national broadcaster TV 2. 

‘It is serious, and I think the threats are unacceptable.’ 

Mr Trump’s intervention has sparked fresh fears he is intent on ripping apart the Western pact that has maintained world peace for the past eight decades.

A man attending an NBA game at London’s O2 Arena yelled ‘leave Greenland alone!’ as actress Vanessa Williams sang the American national anthem before the Memphis Grizzlies and Orlando Magic tipped off on Sunday.

The remark drew a round of applause from the crowd as President Trump continues his saber rattling over the island. 

British MPs also joined the backlash, with calls for the mooted trip by King Charles to Washington in the Spring to be cancelled. ‘The civilised world can deal with Trump no longer. He is a gangster pirate,’ senior Tory Simon Hoare said. 

Running the gauntlet of broadcast studios for the government this morning, Culture Secretary Lisa Nandy stressed that support for Greenland’s sovereignty was ‘non-negotiable’.

‘We believe it is wrong, we believe it is deeply unhelpful,’ she told the BBC’s Sunday with Laura Kuenssberg of Mr Trump’s tariff threat. 

But pressed on the issue of the state visit she merely referred to the ‘depth’ of the Transatlantic relationship. 

Economists have raised concerns that the UK will be back on ‘recession watch’ if the US goes ahead with tariffs. 

Senior MEPs have warned that the EU-US trade deal will be frozen in reprisals, with the spectre of a full-blown global trade war again looming. 

Sir Keir delivered some of his strongest criticism of Mr Trump last night, having expended huge effort trying to maintain warm ties with the President.

The PM said: ‘Our position on Greenland is very clear – it is part of the Kingdom of Denmark and its future is a matter for the Greenlanders and the Danes.

‘We have also made clear that Arctic security matters for the whole of Nato, and allies should all do more together to address the threat from Russia across different parts of the Arctic.

‘Applying tariffs on allies for pursuing the collective security of Nato allies is completely wrong. We will, of course, be pursuing this directly with the US administration.’

Emmanuel Macron also reacted furiously to the news, promising consultation with EU leaders. The French President said: ‘No intimidation nor threat will influence us, neither in Ukraine, nor in Greenland, nor anywhere else in the world when we are confronted with such situations.

‘Tariff threats are unacceptable and have no place in this context. Europeans will respond to them in a united and co-ordinated manner if they were to be confirmed. We know how to uphold European sovereignty.’

Nigel Farage gave a more limited rebuke to the US President, posting on X: ‘We don’t always agree with the US government and in this case we certainly don’t. These tariffs will hurt us.’ 

The Reform leader had been due to appear on the airwaves this morning but was replaced by Richard Tice after being struck down with a heavy cold. 

Mr Tice told the BBC that Mr Trump was worried about China getting a foothold in the Arctic. ‘He’s correct in that, but the approach in the way you work with your closest allies… is completely wrong,’ he said.

He added: ‘On this the President has got it wrong.’

Former foreign secretary Jeremy Hunt said he did not believe Mr Trump would follow through on invading Greenland.

‘To invade the sovereign territory of a Nato ally would mean the end of Nato… it would dissolve that alliance overnight,’ he told the BBC.

However, Mr Hunt acknowledged that it would be ‘squeaky bum time’ to see whether Europe could hold out. 

Tory peer Lord Hannan said: ‘This is demented. Outright batsh** crazy. Where are the adults in the room? Why will no one rein him in?’ 

John Bolton, Mr Trump’s former national security adviser, said: ‘Donald Trump’s extraordinary tariff threat against the UK and other countries for things they have said or done regarding Greenland is without doubt his most dangerous and destructive assertion during the five years of his presidency.

‘To say it is without precedent radically understates how foolish and contrary to fundamental American interests it is. Its ramifications for the special relationship and Nato alliance – indeed for the credibility and trust the United States has spent decades trying to establish – is incalculable.’

The UK already pays a 10 per cent tariff on some goods imported by the US, after Mr Trump introduced a wave of taxes on countries around the world on his ‘Liberation Day’ last April.

Mr Trump’s announcement is the latest twist in the White House’s new foreign policy strategy – dubbed the ‘Donroe Doctrine’ after the earlier Monroe Doctrine – in which it seeks to dominate the western hemisphere and prevent foreign control of vital assets.

The UK has deployed just one military officer, at Denmark’s request, to Greenland to join a reconnaissance group ahead of an exercise named Arctic Endurance.

Mr Trump has insisted the US needs to acquire Greenland for national security reasons and has not ruled out using military force. He has claimed it is vital for his planned missile defence shield known as the Golden Dome.

However, critics claim his interest is linked to Greenland’s untapped mineral wealth rather than defence. The island possesses at least 25 of the 34 raw materials considered ‘critical’ by the EU.

A meeting at the White House last Wednesday, led by Vice President JD Vance with representatives from Denmark and Greenland, ended in an impasse.

Yesterday, thousands of protesters took to the streets in Denmark and in Greenland’s capital Nuuk, chanting ‘Greenland is not for sale’ amid anger over the threats. 

Mr Trump is known to be a huge admirer of the Royal Family. Sir Keir wooed him with an unprecedented second state visit to the UK last year, when he was feted with great pomp and ceremony.

The King has been expected to visit the US in April, while a trip by the Prince of Wales has also been pencilled in.