The 21st-century “Far-Right International” appears to bear no resemblance to the Communist International of the 20th. There’s no modern equivalent of Stalin sitting in the Kremlin and ordering every communist in the world to parrot the same slogans. Yet in Europe and Trump’s America, the far right marches in step towards the same dark destination, as if an invisible high command were directing it.

Concern for free markets and free societies has long gone. The Tory press and elements in the Tory parliamentary party now echo and embellish the conspiracy theories of Putin’s Russia and Orbán’s Hungary. In Britain as in the corrupt outposts of the old Soviet empire, the Jewish financier George Soros is credited with the supernatural power to bring down governments and, in a novel combination of antisemitic and anti-Muslim prejudice, to flood Christian Europe with Muslim refugees.

The most pressing question is the least obvious: why are they descending into paranoid thuggery? Supporters of Brexit ought to be happy. Britain is leaving in March 2019. Theresa May says so. Jeremy Corbyn, the supposed leader of the opposition, isn’t opposing her. All the right has to do is keep its head down and wait for the chance to do as it pleases. Instead, it is being convulsed by neuroticism. So determined is it to destabilise the May government, Brexit could collapse under the stress.

Example. Official government policy set out by the prime minister in Florence was that Britain and the EU would “continue to access one another’s markets” on the “current terms” from when we leave next year until a final deal is concluded. If we did not obey customs union and single market rules in the interim, there would be chaos in every exporting business and at every border. The policy was set or at least we thought it was. But the government is now so terrified of the Tory right accusing it of selling out to Brussels it won’t confirm it. Fear of Jacob Rees-Mogg means the once settled transition terms are up for grabs again and no one has a clue what we want from a final deal.

In short, the proceedings of Her Britannic Majesty’s government look like a knife fight in a lunatic asylum. About 70 rightwing MPs would rather they stayed that way than accept any compromise. They are consciously risking shifting public opinion against Brexit, and playing with the danger that the longer their demands for absolute purity persist, the greater the chance that the majority in the House of Commons will revolt against Corbyn and May and assert its belief that Britain is betraying its best interests.

I say “consciously” but it is often a mistake to ascribe rational motives to irrational movements. Fraser Nelson, the editor of the Spectator, who has spent more time with Conservative politicians than is good for any man’s wellbeing, sees civil war as simply the default Tory position. “Fish swim, birds fly, Tories tear each other’s lungs out,” he tells me with a shrug.

Remember, too, that these are politicians who have fought for 30 years to take Britain out of the EU. Now they have won, they give every appearance of being psychologically incapable of moving out of opposition to take responsibility for protecting the nation. A telling detail emphasised their irresponsibility. After the referendum, Dominic Cummings, the head of Vote Leave, attempted to wipe his campaign’s website from cyberspace. He wanted no record of the false promises for the future his campaign had made now that it might be held to account.

His dilettantism ought to make supporters of the Leave campaign objects of scorn. But in a process familiar to anyone who has been involved with the Labour left, the conspiratorial mentality brings rewards as well as punishments. On the Brexit right as the Corbyn left, the extremes set the rules. Everyone learns to watch for the accuser who leaps up and with a body shivering with rage points an accusing finger at the apostate. On the right, the heresy-hunter is the Tory press, which performs the policing role social media plays on the left. Five years ago, if you had offered right-wing MPs and newspapers a deal in which Britain left the EU and single market but stayed in the customs union for the sake of trade and peace in Ireland, they would have taken it with delight. The pressure to move to the extreme means they now regard even this modest concession as a crime.

A Hungarian government poster campaign targeting George Soros is stoking antisemitism in the country. Photograph: Attila Kisbenedek/AFP/Getty Images

In these circumstances, you can see why the Telegraph, Mail and Sun tear up the old constraints and turn George Soros from an elderly philanthropist and political donor into a Jewish conspirator with the supernatural power to overturn governments and referendum results. They calculate that few “respectable” Conservatives will challenge them and those who do can be damned. The Brexit campaign was always based on a conspiracy theory and eventually every conspiracy reaches the Jews. You start by saying that economists warning of trouble ahead were bought and sold with Brussels gold and end by gibbering about puppet masters and the Rothschilds.

Ominously, when the Tory right looks across the world, it sees its tactics triumphing. In Hungary, Orbán has gerrymandered the electoral system, subjugated the free press and corrupted business. Orbán is now using his control of the media to persuade Hungarians that Soros is about to take over the country, merely because he funds charities for refugees and the victims of Hungary’s many and varied abuses of human rights. Millions of Hungarians believe him. The British right is as determined to persuade millions of British citizens that opposition to Brexit is not a part of the ordinary arguments of a democracy, but the work of traitors controlled by diabolic puppeteers.

Expect much more in this vein. The logic of its fanaticism dictates that the right must pull ever-shadier tricks to stop the public having a clear view of the pathetic state it has reduced Britain to.