Nancy Pelosi, the Speaker of the US House of Representatives, has warned the UK that if Brexit causes “any harm” to the Good Friday Agreement then it can forget about signing any free trade deal with America.

Speaking at the London School of Economics on Monday evening, the powerful Democrat said the peace in Northern Ireland must not be “bargained away”.

“If there were to be any weakening of the Good Friday accords then there would be no chance whatsoever, a non starter, for a US-UK trade agreement,” she said.

John Bolton, the Donald Trump’s national security adviser, recently said the UK would be “at the top of the queue” for a post-Brexit trade deal.

But Pelosi, who will also travel to Ireland this week, warned it was not just up to the White House.

She said: “First of all let me say it’s very hard to pass a trade bill in the Congress of the United States, there is no given anyway.”

She added the Good Friday Agreement was more than a treaty as it was a “model to the world” and “something we all take pride in”.

“It was hard. But it was a model. And other people have used it as model. And we don’t want that model to be something that can be bargained away in some other agreement,” she said.