It is now beyond any reasonable doubt that the Russian state is behind the terrible attacks in Wiltshire, and the life-threatening injuries inflicted not only on Sergei Skripal and his daughter Yulia, but also on a local police officer, Nick Bailey, going about his duty. The method of the attack and the substance used leave no doubt, and the existence of a clear motive and previous form with this type of attack hardens the case further.

Moreover, the contemptuous reaction from the Russian state since then shows a complete lack of respect for international relations and the rule of law.

Given the nature and severity of the attack, it is right that the government has responded in proportionate and robust terms. By expelling 23 FSB officials, masquerading under diplomatic colours, we will hopefully erode the Russian state’s ability to pursue its espionage and assassinations on British soil.

By cancelling ministers’ tickets to the World Cup, and by encouraging the royal family to stay at home too, we send an important signal to the world that we will not tolerate this state-sponsored terror and we will not legitimise Putin’s regime with a celebration of the world coming together on his turf. From Russia’s malign interference and attempts to stoke division in western democracies to its complicity in the use of chemical weapons against civilians in Syria, it has become increasingly brazen. A firm stand has to be taken before this escalates even further.

Foreign powers such as the Russian state respect strength from their adversaries, they thrive on weakness

I disagree with Theresa May on virtually every domestic issue, and dedicate my every waking moment to defeating her government and replacing it with a Labour government. That’s what my constituents in Redcar expect and deserve. But when it comes to Britain’s safety and security, and our place on the world stage, there are points of agreement. One of these is how to deal with Russia.

There are important precedents for this. Clement Attlee gave Churchill the full support of the Labour opposition in 1940, and formed part of the wartime coalition to defeat the Nazis. In 1982, Michael Foot stood at the dispatch box in parliament as leader of the opposition and gave a memorable speech in support of Thatcher’s resolution on the Falklands. When British national interests are threatened by foreign powers, the Labour and Conservative front benches have usually spoken with one voice.

This is vital because foreign powers such as the Russian state respect strength from their adversaries. They thrive on weakness. They especially draw succour from division. If they can sow discord and split British public opinion and the British parliament, they consider it a job well done.

So I hope that Labour’s response will echo the words of our shadow defence secretary, Nia Griffith, who says the finger of blame is clearly pointing at Russia. She reminds us that Labour’s frontbench has been fully briefed by the security services and government officials with the latest intelligence. And, like me, she offers Labour’s support to the prime minister as she acts in Britain’s national interest on the world stage.

Winston Churchill once gave a useful piece of advice to a new member of parliament: the first duty of an MP is to do what is right and necessary for the honour and safety of Great Britain. And our second duty is to our constituents. In times of national emergency, and this is one, we would do well to remember Churchill’s formula. By backing May, Labour MPs are doing what is right by both their country and their constituents. Today Wiltshire, but tomorrow who knows which town or city might be the backdrop to Russia’s chemical warfare?

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There will be those who want to absolve Russia from any blame. Or those who want to construct elaborate conspiracy theories about the real culprits, and “false flags”. Or those who hate the west, want to denigrate our security services and distrust the Tories. But now is not the time for such indulgences. It is not the time for party politics. What the world needs to see is a Britain united in condemnation and resolute in action, and a strong response from the top, starting with the government and echoed throughout parliament. That is what I will be urging my colleagues to do as we enter a deadly and dangerous period of international diplomacy.

• Anna Turley is the Labour and Co-operative MP for Redcar