Peter Oborne writes:
Let's try a mental experiment.
Let's imagine that the Russian embassy had been caught red-handed drawing up a "hit list" of British MPs it wanted to take down.
Let's further assume that the hit list included a senior minister in the British foreign office known for his deadly criticisms of Vladimir Putin.
And that a second figure on the list was another critic of Russia, the influential chairman of the Commons Foreign Affairs Committee, once again targeted for his anti-Russian opinions.
Let's assume also that a Russian official had been filmed telling the chairman of the Labour Friends of Russia that he had obtained "more than £1m" - say $1.2m - to pay for sympathetic Labour MPs to travel to Russia.
All hell would have broken loose.
The Russian ambassador would have been summoned to the Foreign Office to explain himself.
The embassy official would certainly have been frog-marched onto the next plane home.
We would have heard threats of sanctions and the breaking of diplomatic relations.
A full-scale diplomatic crisis would have erupted.
The British prime minister, Theresa May, would have demanded a personal explanation and apology from Putin.
Substitute "Israel" for "Russia" and it's a very different story.
No expulsions. No diplomatic row. No threat of sanctions.
Business as usual.
We have been blandly informed that the Israeli ambassador has apologised to Alan Duncan.
The British foreign office has issued a brief statement saying that the UK has "a strong relationship with Israel and we consider the matter closed".
There's a stench here. Something is badly wrong. Nothing adds up.
This episode raises a number of burning questions concerning British national security, not one of which have been answered.
First and foremost, who in reality is this Israeli embassy official Shai Masot?
We are told that, even though he operates out of the Israeli embassy, he is not a diplomat.
If he's not a diplomat, what is he?
The Israeli embassy says that Major Masot (he apparently describes himself as an officer in the Israeli Defence Forces) is a nothing more than a junior figure who spoke out of place.
We should not blindly accept this assertion.
Indeed we should not accept this assertion at all.
Masot is handling very large sums of money – more than £1m for Labour Friends of Israel alone if the tapes are to be believed.
The tapes, the result of months of undercover filming by Al Jazeera, appear to show him meddling very deeply with both main parties in the heart of British politics.
His activities are absolutely consistent with the kind of covert influence campaign of which Russia has recently been accused in the United States.
This improper interference in the politics of another country is unacceptable whether it comes from Russia or an ally such as Israel.
Indeed the fact that Britain and Israel are such close allies does not improve matters.
It makes them much worse. Israeli politicians and diplomats have very privileged access in this country.
They share all kinds of secrets, and they have access to anybody they like.
It is a gross abuse of confidence and trust if they are simultaneously engage in conversations about "taking down" British politicians who do not share their outlook.
Today senior British MPs have come out and demanded a full-blooded government investigation.
One of them is Sir Nicholas Soames, the grandson of the great wartime leader Sir Winston Churchill and himself a former defence minister.
When I spoke to him today, Sir Nicholas compared the activities of the Israelis to the KGB.
He told me: "This ranks as the equivalent of Soviet intelligence in what they are doing to suborn democracy and interfere in due process."
Shadow foreign secretary Emily Thornberry rightly noted that this is a "national security issue".
As such it demands a very serious investigation.
We need to know if Masot took any concrete steps to damage Alan Duncan, the deputy foreign secretary, and Crispin Blunt, the foreign affairs committee chairman.
Have any other British MPs been targeted by the Israelis?
What did Israeli Ambassador Mark Regev know about Masot's activities?
And if he didn't know, why not?
Crucially, we need to know where Masot got the £1m for Labour Friends of Israel?
What other sums has he dispensed to British political organisations?
Have individual payments been made to MPs and others?
How effective has Masot been in shaping political discourse in the UK?
If any other country had been involved in this kind of operation – and that includes allies such as France, Saudi Arabia or the United States – we would urgently need to know the answer.
Israel may be an ally, but it is no exception.
There is one other extremely serious point to consider.
If Britain does not investigate this Israeli malpractice, we simply give the green light to further covert operations of this sort on British soil.
Finally, mystery surrounds the reaction of the Foreign Office.
Within hours of the story breaking it announced that the issue was "closed".
Why? How did it reach this conclusion so quickly?
Is Theresa May's government complicit in Israeli interference in the British democratic process?
Masot, we now know, believes that Foreign Secretary Boris Johnson is an "idiot".
If Johnson has an ounce of patriotism, he needs to wake up very fast, get to grips with an outrageous interference with British democracy and announce a serious investigation.