We should have known the way things were going when the Conservative press tried to smear Jeremy Corbyn as Cold War-era Czech spy. Now, after a likely Russian nerve gas attack on ex-spy Sergei Skripal, there are cries of ‘traitor’ just because the Labour leader dared to ask for conclusive evidence.

Not for the first time, by asking the right questions at the right moment Corbyn has demonstrated he understands the time-value of information: that what is presented as cast iron truth today can turn out, tomorrow, to be less defensible, destroying trust in politics and democracy itself. More importantly, at a time when Britain is isolated in its response to the attack, Corbyn’s approach demonstrated a grasp of the global power balance more mature than many of the Brexiteers who were jeering him from the Tory benches.

What are the facts? The Skripals were attacked, injuring a police officer and endangering the lives of tens of other bystanders. Porton Down says the nerve agent was Russian-made. If so, as Theresa May said on Monday, either the Russian government deliberately used the agent to send a very scary message to the UK, or they lost control of it. Either way, they have broken international law and deserve to be punished, isolated and dissuaded from such action in the future.

I have no hesitation in accepting that version of events.

Today May went further, saying the Russian government’s failure to meet her own deadline for an explanation meant: “There is no alternative conclusion other than that the Russian state was culpable”.

It was Corbyn’s request for the evidence backing that judgement that produced the current hue and cry, both from the Tories and from habitual warmongers on Labour’s backbench.

Britain stands in a precarious position. We are isolated – with solidarity from other countries half-hearted and gestural to say the least. And Corbyn’s questions – amounting to where’s the evidence, and can we take our complaint to a globally accredited agency – go to the heart of why.

In 2008 Vladimir Putin broke from the multilateral global order during the Georgia war. He escalated that break first by direct intervention into the Syrian conflict, then by annexing Crimea and parts of Ukraine. Then by conducting hybrid warfare against all western democracies, including the pollution of social media with fake news, hate speech and direct meddling in elections – culminating in the victory of Donald Trump.

Throughout this entire time the Tories made sure London was the number-one destination for the pro-Putin Russian billionaires to keep their money, and for the ill-gotten gains of the Russian mafia to be laundered through our finance system.

That is why £3m worth of donations have come from Russian donors to the Conservative party – and why despite calls for a UK version of the Magnitsky Act, which allows the targeting of regime-friendly individuals for financial sanctions, the Tories opposed it.

The pro-Putin section of the Russian elite has become intertwined with the British financial elite – not just through hedge funds and nightclubs – but law firms, property firms, accountancy firms and football clubs. The money thrown at the Conservative party was there to achieve what it has achieved: a blind eye turned to what look like 14 suspicious deaths of Putin’s opponents – and no laws along the lines of the US Magnitsky Act.

The existence of London as bolt-hole, money laundering venue and bank for the pro-Putin elite is not incidental to the way the regime operates. It is essential. Because it knows nothing bad will ever happen to its money in Britain, the Russian business elite allows Putin to act like a semi-fascist dictator at home, in Syria and in the countries he has invaded.

Corbyn’s line of attack focused on:

The need for a Magnitsky Act The need for evidence The need for due process, not just in the British justice system but in the UN and the OPCW

This is exactly the approach that would have prevented Britain going to war in Iraq, and prevented the security establishment under Tony Blair from manipulating intelligence to achieve an unjust and unnecessary conflict.

Just as Putin has form in murdering people through disgustingly cynical means, unfortunately the British state too has form in manipulating secret intelligence.

On top of that, there is a practical problem – and that’s the divided state of our potential allies. If we start nearer to Russia: Hungary is ruled by a party sympathetic to Russia; Austria has governing coalition where the far-right, the FPÖ, actually has a formal alliance with Putin’s United Russia party. Italy just had elections where the Five Star Movement – a party very positive towards Putin – won 33%. Inside Germany there is, unfortunately, strong sympathy with Putin inside the Social Democratic party and strong antipathy to confronting Putin across most sections of society. Oh, and in the US the president was, for the first 12 months, surrounded by people now under investigation for their links to the Kremlin.

On the British left there is, of course, a minority of people prepared to believe anything Putin says and echo the Russian troll farms’ theories about ‘false flags’, and regurgitate fake news. Their fantasies are fuelled by the Kremlin mouthpiece media Russia Today (RT) and Sputnik, which long ago ceased to observe even a modicum of respect for the truth.

For the first few days after the attack they were silent – but not now: my Twitter timeline is buzzing with accusations that I, by criticising Russia, am a neo-con, a mass murderer, a Zionist and the rest.

The best weapon against these assholes is truth. The best weapon against an asshole like Putin is evidence. The best way of building a coalition against him is restraint and prudence and due process. That’s what Labour is asking for.

Theresa May is right to expel some diplomats. But she didn’t do what her own screeching party wanted – shut down RT or begin asset seizures. She did propose a law change that would allow Russian spies to be turned away at the border – and we need to see the detail of that.

But let me explain the worst case scenario. If Putin really did order the Skripal attack using nerve gas as a matter of state policy, that is a big signal. It says: the West is so divided, Europe so weak, Trump so in my pocket that I can do anything I want to.

What he wants is fairly well-known: to remove the pro-Western government of Ukraine, returning it to satellite status of Russia; and to neutralise Nato in the Baltic. He also wants a free hand for his recently constructed alliance in the Middle East, which includes Iran, Syria, Hezbollah and influences the behaviour of both Egypt and Turkey.

There is a possibility that this attack may be a mistake, or a freelance job by lower echelons of the Russian secret state, or an election stunt, or even organised criminals using old stocks. But if, instead, it is a calculated chess move, then it’s a terrifying one. It would have to be seen as testing out the West for a bigger move – either against Ukraine or the Baltic.

This is what Putin calls the “multipolar world” – and unfortunately it is becoming a reality. The reason is that the old, unipolar order guaranteed by the USA has fallen apart, and the USA itself has become an unstable democracy. Last week Putin made a speech demonstrating his willingness to use armed force and nuclear weapons to achieve Russian security within a multipolar world.

So everything Britain does needs to demonstrate two things: strength and sustainable alliances. If the Salisbury attack really is the starting pistol of a new and dangerous gambit by Putin in Europe, what you’d need in parliament is real bipartisanship: that is the acceptance of differences of opinion, differences of interpretation and tactics, and differences in appetite to seek confrontation.

Yes I am annoyed when I hear left-wing people defend Putin, or ascribe all attacks on him as conspiracies. But I am also annoyed when I see the Tories trying to weaponise ‘loyalty’ over the Russian issue, stigmatising Labour as traitors.

Theresa May is a burned out politician who will be gone probably in a few months – she can afford to be wrong now. Jeremy Corbyn wants to govern the country: what he says today has to hold good in 12-24 months time, and the alliances he constructs with a very shaky set of western democracies have to last.