The diplomatic nightmare presented to Sir Keir Starmer by Donald Trump’s victory deepened last night when it emerged that he called for an export ban on Trump’s America after he became Labour leader.

Sir Keir – who insists that he ‘looks forward’ to working with the US President-elect – made his demand in a letter to Boris Johnson in 2020, after the death of George Floyd at the hands of US police triggered the Black Lives Matter protests.

It is one of a series of embarrassing remarks made by the Prime Minister and his senior ministers which have emerged in the wake of Trump’s landslide win.

In the letter, sent to the then-Prime Minister Johnson on June 4, 2020, Sir Keir said Floyd’s death had ‘shone a spotlight on the racism, discrimination and injustice experienced by those from black and ethnic minority communities in the US’.

He asked: ‘What review is the Government conducting to ensure UK exports are not being used in the suppression of democratic rights?’

His question related to British exports of riot control weapons and equipment to the US including anti-riot guns, tear gas and shields.

In other remarks made since becoming leader, Sir Keir disparagingly described Mr Johnson as ‘Britain’s Trump’, said the previous Trump administration sought a trade deal with the UK ‘to benefit America’s big healthcare companies’ and questioned Trump’s ability to lead the world’s response to coronavirus.

In May 2020, he said: ‘I don’t think in President Trump we’re seeing the man capable of pulling the world together with a global response.’

Prior to becoming party leader he was even more critical, saying in June 2019: ‘An endorsement from Donald Trump tells you everything you need to know about what is wrong with Boris Johnson’s politics and why he isn’t fit to be Prime Minister.’

In 2018 – a year after his wife Victoria was pictured at an anti-Trump march with a ‘down with Trump’ sign – he posted: ‘Humanity and dignity. Two words not understood by President Trump. A truly ‘great country’ treats all people with humanity and dignity.’

In 2016, during a parliamentary debate on banning Trump from the UK, Sir Keir said: ‘Much of what he says is deeply offensive’.

And as recently as last year, he accused the Tories of no longer being ‘Churchill’s Tories’, instead becoming ‘more and more like Donald Trump’.

Foreign Secretary David Lammy has been backpedalling rapidly from comments made before taking office in which he called Trump ‘a tyrant in a toupee’, ‘deluded, dishonest, xenophobic, narcissistic’ and ‘a woman-hating, neo-Nazi-sympathising sociopath’. Health Secretary Wes Streeting called him ‘an odious, sad, little man’.

Environment Secretary Ed Miliband said he was ‘a racist, misogynistic self-confessed groper’.

The damage to the so-called ‘special relationship’ has been compounded by the Trump campaign registering an official complaint after Labour activists campaigned against him in the US.

It has led to the Foreign Office hitting the panic button – by preparing to roll out the Royal Family to soothe diplomatic tensions.

Yesterday’s Daily Mail reported that diplomats are planning to play their ‘Trump card’ by counting on King Charles to become a ‘key asset’ in forging a positive relationship with the new President.

They described the family as a ‘priceless and powerful’ weapon of soft-diplomacy. Charles and Mr Trump have met twice.

Officials say that, while they hold strong differences of opinion over issues such as climate change, they have a ‘warm bond’.