Labour leader Jeremy Corbyn is a crazy politician surrounded by weirdos and extremists, Boris Johnson - the foreign secretary - is an idiot whose deputy Alan Duncan should be taken down, and Crispin Blunt is among a group of MPs that are strongly pro-Arab rather than pro-Israel.

This all according to Shai Masot, who last year introduced himself to Al Jazeera's undercover reporter Robin Harrow (alias), as a senior political officer at the Israeli embassy in London.

Masot, who was at the centre of Al Jazeera's six-month investigation "The Lobby", resigned earlier this week following the release of the damning footage involving the embassy official on Sunday.

Al Jazeera Investigations' story of the Israeli government's brazen, covert influence campaign in Britain gained significant attention after being published by international media from The New York Times and The Guardian to Le Monde and Haaretz.

The front page of Britain's Mail on Sunday read: "Israel plot to 'take down' Tory minister", referring to Masot's plans to unseat Duncan.

Inquiry urged

Parliamentary officer Maria Strizzolo, Masot's associate who hinted that she hoped "a little scandal" would bring Duncan down, also quit her job soon after the story broke.

Reports of Israeli embassy official discussing how to discredit government minister disturbing @EmilyThornberry https://t.co/UO7LJcMlbe — Labour Press Team (@labourpress) January 8, 2017

Senior politicians have raised concern over Masot's comments, which apparently targeted Duncan for being a critic of Israel's settlement policy in the occupied West Bank.

Corbyn, leader of the opposition, on Friday, called on Theresa May, the British prime minister, to launch an inquiry. "This is clearly a national security issue," he wrote in a letter shared with media.

He describes the actions of Israeli embassy official Shai Masot as "improper interference in this country's democratic process".

Labour politician Emily Thornberry, who describes herself as both a friend of Israel and Palestine, called on the government to "launch an immediate inquiry into the extent of this improper interference and demand from the Israeli government that it be brought to an end".

Scottish National Party MP Alex Salmond also backed an official investigation "so that we can be confident our elected officials are free to carry out their jobs to the best of their ability and without fear of having their reputation smeared by embassy officials who do not agree with their views".

READ MORE: UK MPs urge probe into Israeli plot against politicians

The investigation also revealed how supporters of Corbyn, a leftist with a long history of Palestinian solidarity activism, were among those accused of anti-Semitism by Israeli officials.

The pro-Israel lobby in Britain attempted to smear activists who question the illegal occupation of Palestinian land by helping to build racism cases against them, Al Jazeera Investigations found.

Boris Johnson: Matter closed

Despite some calls for an official probe, Johnson rejected calls to discipline Israel over Masot's plot.

Speaking in the House of Commons on Thursday, Johnson said: "Whatever he [Masot] may exactly have been doing here his cover may well be said to have been ... truly blown - so the matter can be considered closed."

"The Takedown", the fourth and final episode of "The Lobby", features the damning conversation at a London brasserie that led to Masot and Strizzolo's resignations.

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The extent to which the embassy influences the Labour Friends of Israel (LFI) parliamentary group with strategic and financial support is also revealed.

Robin is told by pro-Israel activist and parliamentary officer Michael Rubin that, according to Masot, "the Israeli embassy will be able to get a bit of money" to establish an LFI offshoot for young people.

Throughout the investigation, Robin posed as a graduate activist with strong sympathies toward Israel, eager to help combat the growing Boycott, Divestment and Sanctions movement.

'Deliberate interference'

At one point, Masot offered Robin a leading role in setting up the youth branch of the LFI, introducing him to members of the pro-Israel lobby as the new chairman of the group.

British journalist and author Peter Oborne, who has researched the pro-Israel lobby in the UK, told Al Jazeera: "If you were trying to fool the British people by setting up a front organisation which masquerades, or says that it is genuine Friends of Israel, but actually is run from Tel Aviv, that's troubling.

"Just imagine it being sort of apparently spontaneous pro-Iranian organisation in Britain and it turned out that it was run from Tehran or inspired by Tehran. That will be outrageous."

Oborne described as "shocking" the exchange between Masot and Strizzolo, relating to "taking down" Duncan.

"This is a clearly deliberate attempt by a foreign government to interfere in the workings of British democracy and to secure the destruction of the career of a minister in the British government," he said.

All four parts of "The Lobby" are available to watch online.