A video has emerged that appears to show world leaders joking about Donald Trump at the Nato summit in London, which has been marked by sharp disagreements over spending, future threats including China and Turkey’s role in the alliance.

The footage shows leaders including Boris Johnson, Justin Trudeau and Emmanuel Macron at a function at Buckingham Palace on Tuesday evening. Johnson asks Macron: “Is that why he was late?” before Trudeau interjects: “He was late because he takes a 40-minute press conference off the top”.

Trudeau adds: “Oh, yeah, yeah yeah. He announced … ” before he is cut off by Macron, who speaks animatedly to the group. Macron’s back is to the camera and his words are inaudible.

It is never said whom the group are talking about, but the exchange appears to refer to the US president, who is known for his long, rambling press conferences and who had an unscripted 50-minute back and forth with reporters on Tuesday.

As he did at last year’s Nato meeting, Trump has thrown out normal summit protocol and used his appearances with allied leaders to field dozens of questions from the world’s media.

Top of the agenda on Wednesday is Turkey’s threat to block a Nato plan for the defence of the Baltics and Poland unless Nato denounces the Syrian Kurds, and by extension endorses the Turkish incursion in October into north-east Syria.

Facebook Twitter Pinterest Leaders including Boris Johnson, Donald Trump and Recep Tayyip Erdoğan gather for the family photo at the Nato summit in London on Wednesday. Photograph: WPA Pool/Getty Images

The Queen hosted world leaders at a reception at Buckingham Palace on Tuesday night to mark 70 years of Nato cooperation, as protesters gathered outside, rallying against Trump and his perceived interest in the NHS in a US-UK trade deal and Nato.

After an edited cut in the film, the footage later shows an incredulous Trudeau telling the group, which also included Mark Rutte, the prime minister of the Netherlands, and Princess Anne: “You just watched his team’s jaws drop to the floor.”

Again, it is not known whom the group are talking about, and none of the world leaders appeared to realise the conversation was being recorded.

The pool footage available to all broadcasters was posted online and then edited by the Canadian Broadcasting Corporation to focus on the interactions between the leaders, with the audio cleaned up and subtitles added.

The footage emerged after a day when Nato disunity was on full display, as Macron accused Turkey of colluding with Islamic State proxies, and Trump described Macron’s criticisms of Nato’s “brain death” as insulting and “very, very nasty”.

Facebook Twitter Pinterest The Nato group photo. Photograph: WPA Pool/Getty Images

On Wednesday, Trump is scheduled to meet the German chancellor, Angela Merkel, and the prime minsters of Denmark and Italy. He is also due to give another news conference, this time on his own, after the 29 Nato leaders hold a full three-hour closed-door summit session and issue a statement to celebrate their supposed unity.

The Turkish president, Recep Tayyip Erdoğan, has threatened to hold up Nato efforts to bolster the protection of the Baltic republics against Russia unless the allies brand the Kurdish militias who defeated Isis in Syria as “terrorists”.

Amid fears Erdoğan could even veto the summit declaration and with barely two hours to go before the leaders sat down for their sole roundtable discussions, the Nato secretary general, Jens Stoltenberg, admitted a solution to the issue had still not been found.

“I’m confident that we will be able to find a solution to the issue related to updating the revised defence plans,” Stoltenberg said as he arrived for the summit at a luxury golf hotel on the outskirts of London. “I discussed this with President Erdoğan last night and we are working on the issue as we speak.”

Johnson played down the dispute. “There is far, far more that unites us than divides us, and I think one thing every leader here is absolutely resolved upon is the vital importance of Nato for our collective security,” the prime minister said as he arrived.

• Note added 11 December 2019. This article was amended on 4 December 2019 to: clarify that the video of the leaders talking was from pool footage available to all broadcasters; and to remove an ambiguous reference which gave the mistaken impression that the Russian state’s media entity, Sputnik, had been the source of the footage which other media, including the Canadian Broadcasting Corporation, had used.