A banner proclaiming “I crashed the economy” featuring a picture of a lettuce forced Liz Truss from the stage at an event in Suffolk on Tuesday night.

Speaking at Beccles Public Hall and Theatre to promote her book Ten Years to Save the West, the former prime minister was discussing her support for Donald Trump when the banner unfurled behind her.

Once Ms Truss noticed the sign, which political campaign group Led By Donkeys took credit for, she said “that’s not funny” before picking up her papers and leaving the stage to a smattering of applause.

Led By Donkeys confirmed the event was genuine, but refused to explain how they pulled the stunt off.

Ben Stewart, co-founder of Led By Donkeys, who attended the event on Tuesday, told the PA news agency: “This is all about Liz Truss aligning herself with Trump and the far right in America.”

He said: “She’s avidly supporting Trump, and actually she’s lending the weight of the office of British Prime Minister which she held, albeit for a short period of time, to the pro-Trump campaign.

“We thought, she’s aligning herself with the far right in America, and sometimes, not always, but sometimes, one of the best approaches to the far right is to laugh at them.

“And so we decided to install this strategically positioned remote control lettuce banner and press the button towards the end of last night’s event.”

Ms Truss was in the middle of discussing American politics, saying “I support Trump and I want him to win” before the banner unfurled.

As it descended she said: “It’s what I was saying a bit about incumbents, the average American is not doing well, and people do vote on… I think it was Bill Clinton’s adviser who said ‘it’s the economy, stupid.’ So I think that he will probably win.”

Ms Truss only lasted 44 days as leader of the country – she famously was outlasted by a lettuce that was recorded on a live stream, created by the Daily Star, which asked: “Which wet lettuce will last longer?” referring to the Prime Minister and an actual lettuce.

Once she had been alerted to the sign behind her, the former prime minister was clearly unhappy and left the stage.

Mr Stewart said she did not return.

“We just wanted to remind people, do not take this person seriously,” he said.

Ms Truss’s office declined to comment.

A spokesperson for Beccles Public Hall and Theatre said the venue is assisting the police.