Britain remains committed to the Iran nuclear deal despite Benjamin Netanyahu’s claims that Tehran has been deceiving the world about its weapons programme.

The Israeli prime minister used an elaborate presentation on Monday evening to say Mossad had discovered 55,000 pages of documents that demonstrated the landmark 2015 nuclear deal was “built on a lie”.

The deal, known as the Joint Comprehensive Plan of Action (JCPOA), faces a key deadline next week when US President Donald Trump decides whether or not to abandon it.

It was signed in 2015 between Iran, the UN Security Council’s permanent members and Germany.

Mr Trump has been a long-time critic of deal but other signatories, including Britain, want to retain it.

Foreign Secretary Boris Johnson said: “The Israeli Prime Minister’s presentation on Iran’s past research into nuclear weapons technology underlines the importance of keeping the Iran nuclear deal’s constraints on Tehran’s nuclear ambitions.

“The fact that Iran conducted sensitive research in secret until 2003 shows why we need the intrusive inspections allowed by the Iran nuclear deal today.

“That is another good reason for keeping the deal while building on it in order to take account of the legitimate concerns of the US and our other allies.”

Mr Netanyahu’s televised remarks in English featured a PowerPoint presentation, video and stage props.

He said Project Amad was the codename for the programme and revealed the documents had been seized in recent weeks from a run-down warehouse in Iran.

“Now, from the outside, this was an innocent looking compound,” Mr Netanyahu said about the warehouse, adding “but from the inside, it contained Iran’s secret atomic archives locked in massive files.”

An International Atomic Energy Agency spokesman declined to respond to Mr Netanyahu’s accusations.

His findings were immediately ridiculed by the Iranian regime. Mohammad Javad Zarif, foreign minister, said: “The boy who can’t stop crying wolf is at it again.”

But Mr Trump, speaking after the presentation, said: “What we’ve learnt has really shown I’ve been one per cent right.”

In a statement, Secretary of State Mike Pompeo added: “The documents obtained by Israel from inside Iran show beyond any doubt that the Iranian regime was not telling the truth.

“We assess that the documents we have reviewed are authentic. Iran hid a vast atomic archive from the world and from the International Atomic Energy Agency (IAEA) - until today.”