Former EU Council chief Donald Tusk fired a shot at Donald Trump today by tweeting a photo of himself pretending to point a gun into the back of the US president.

The ex-European Council chief waded into the diplomatic row which blew up at this week's Nato summit after Justin Trudeau and Emmanuel Macron were caught mocking Trump behind his back.

After the President stormed from the gathering of heads of government in London last night, Tusk appeared to heap yet further ridicule on the humiliated US leader by sharing a picture of himself purportedly mimicking to press a handgun into Trump's back.

The photo of the two Donalds - who had an icy relationship during the Brussels politician's term at the top of the EU - was taken at last year's G7 meeting in Canada.

But by sharing the controversial picture in the wake of Trump's awkward Nato summit, Tusk has taken a blatant swipe at the reeling US leader.

The ex-Polish PM, who stepped down from his EU role last week, tweeted from his personal account to his 6,800 followers with a message of transatlantic unity.

Alongside the image Tusk wrote: 'Despite seasonal turbulences our transatlantic friendship must last #Trump #NATO.'

The intervention ratchets up his feud with the President, who he regularly took aim at during his tenure as EU Council chief.

Only a few months ago, Tusk used a United Nations speech to slam the President's views as 'false and dangerous'.

Donald Tusk tweeted a picture of him pointing two fingers into the back of President Trump

Alongside the picture, former EU Council leader Donald Tusk tweeted a message of transatlantic unity

European Council President Donald Tusk waving as he leaves the European Council headquarters in Brussels last month

The photo of the two Donalds - who had an icy relationship during the Brussels politician's term at the top of the EU - was taken at last year's G7 meeting in Canada (from left to right: Donald Tusk, Theresa May, Angela Merkel, Donald Trump, Justin Trudeau, Emmanuel Macron, Shinzo Abe, Giuseppe Conte, Jean-Claude Juncker)

And in 2018 he called the White House administration 'capricious' and said: 'Looking at the latest decisions of President Trump, some could even think, "with friends like that, who needs enemies?".'

Germany's Angela Merkel was seen looking on in the picture, although it is unclear whether her reaction to the stunt was positive or negative.

Tusk and Trump's war of words September 2019: Tusk uses a UN speech to slam the President's views as 'false and dangerous'. August 2019: Tusk blasts Trump's wish for Russia to rejoin G7 was a 'business calculation'. July 2018: After Tusk reminded Trump to remember who his friends are - a veiled swipe - , the outraged President hit back: 'NATO countries must pay MORE, the United States must pay LESS. Very Unfair!' May 2018: Tusk calls the White House administration 'capricious' and questioned the alliances Trump was building. Advertisement

Tusk, who was head of the European Council from 2014 until last month, now leads the centre-right European People's Party.

Trump seemed unaware of Tusk's gesture and as of this afternoon has not tweeted about his EU counterpart's post, which was the second time the president was mocked by a world leader at the summit.

The US president cancelled his last press conference at the NATO summit after four leaders were caught on a 'hot mic' appearing to mock his lengthy press briefings.

Emmanuel Macron, Boris Johnson and Justin Trudeau were caught at the Queen's reception talking with Dutch Prime Minister Mark Rutte about the US president's staff and their reactions to some of his antics.

In the video from the reception, which appears to be edited, Trudeau and the other leaders are seen chuckling about Trump while Princess Anne watches on.

After watching the viral clip, Trump tweeted that he would leave the summit without holding a scheduled press conference, bringing an acrimonious end to the military alliance's 70th anniversary gathering.

President Donald Trump at a breakfast meeting with Nato Secretary General Jens Stoltenberg at Winfield House in London on Tuesday

Justin Trudeau, center, Emmanuel Macron, second right, and Boris Johnson, right, have all been caught on a hot mic at the Buckingham Palace NATO reception appearing to gossip about Donald Trump and an apparent impromptu lengthy press conference

The President wrote: 'When today's meetings are over, I will be heading back to Washington. We won't be doing a press conference at the close of NATO because we did so many over the past two days.'

He then blasted Trudeau as 'two-faced' over Canada's payment towards NATO.

Trump told reporters, in yet another press appearance, this time before his head-to-head with German Chancellor Angela Merkel.

'With Trudeau, he's a nice guy. I find him to be a nice guy, but the truth is, I called him out on the fact that he's not paying two per cent and I guess he's not very happy about it,' he said.

At around 5pm he boarded Marine One at the Grove Hotel in Watford and flew to the runway where Air Force One was preparing to take off.

Since taking office Trump has repeatedly denigrated the EU, once describing the bloc as a 'foe' when asked which nations or leaders he considered to be adversaries of the US.

In the clip, Trudeau makes the most cutting comments, laughing about Trump's lengthy Q&A sessions with reporters and saying even the president's staff was shocked at some of his actions

A tense meeting between Donald Trump and Justin Trudeau was captured on camera at the NATO summit in Watford, Hertfordshire on Wednesday after Trump was questioned by reporters about Trudeau's comments caught on a hot mic on Tuesday

Last week Tusk branded President Trump as possibly the greatest challenge for the European Union in a German newspaper column.

He wrote in Die Zeit: 'For the first time in history, there is an American president who is openly against a united Europe. He supports Brexit and prays for the breakup of the Union.'

Since the video was made public, all three leaders, Johnson, Macron and Trudeau all moved to defuse the situation.

Macron raged that the video - said to be captured by freelance cameraman Andy Laurence and handed to broadcasters before being first aired by the Canadian Broadcasting Corporation - was 'stolen' as cameras should not have been rolling in that room.

Boris Johnson pleaded ignorance saying it was 'complete nonsense. I don't know where that has come from'.

Trudeau insisted they were not ridiculing the president but merely expressing surprise he chose to announce details of an upcoming G7 summit.