It is understood that switching off the escalators and lifts would suggest the organisation had run out of money. And when the Trumps visited, the escalators are said to have been working perfectly until Melania set foot on one.

It meant the couple had to walk up stalled steps. Trump later worked the incident into his speech, saying Melania would have “fallen” if she “wasn’t in great shape”.

He said: “If the first lady wasn't in great shape, she would've fallen. But she's in great shape. We're both in good shape.”

Later added: “These are the two things I got from the United Nations. A bad escalator and a bad teleprompter. Thank you very much.”

Karoline Leavitt, the president’s press secretary, said the UN staffers were “basically plotting to set up” the US President. She told Fox News that “the audio inside of the room was much lower and different for the president of the United States than the previous speakers”.

She said: “So when you put all of this together, it doesn’t look like a coincidence to me. And I know that we have people, including the United States Secret Service, who are looking into this to try to get to the bottom of it.

“And if we find that these were UN staffers who were purposely trying to trip up, literally trip up the president and the first lady of the United States, well, there better be accountability for those people, and I will personally see to it.”

A Sunday Times report over the weekend suggested UN figures were overheard “joking” about stunts they could pull on Trump to highlight how his administration withholding cash has led to a funding shortage.

A UN spokesman told The Times that all three incidents were “genuine mishaps”. Spokesman Farhan Aziz Haq said: “Regarding the escalator: The safety mechanism was inadvertently triggered by someone who was ahead of the president on the escalator. The escalator was immediately reset and is in operation.

“Regarding the teleprompter, we have no comment since we don’t operate that teleprompter. The interpretation audio was heard when a non-official interpreter pressed the wrong button, which briefly allowed a non-UN interpreter to be heard.”

Stephane Dujarric, a spokesman for the UN general secretary, believes a US videographer accidentally triggered a “safety function” on the escalator. He believes the escalator stopped working when the videographer reached the top.

He explained the safety feature is designed to “prevent people or objects accidentally being caught and stuck in or pulled into the gearing”.