London (CNN)British Prime Minister Theresa May told Parliament on Monday that it was "highly likely" that Russia was responsible for the attempted murder of former Russian spy Sergei Skripal and his daughter Yulia in the English city of Salisbury on March 4.
Theresa May's full statement on Russian spy's poisoning
Below is her address to the House of Commons in full, released by Downing Street:
With permission, Mr. Speaker, I would like to update the House on the incident in Salisbury -- and the steps we are taking to investigate what happened and to respond to this reckless and despicable act.
Last week my Right Honorable Friends, the Foreign and Home Secretaries, set out the details of events as they unfolded on Sunday the 4th of March.
I am sure the whole House will want to once again pay tribute to the bravery and professionalism of our emergency services and armed forces in responding to this incident, as well as the doctors and nurses who are now treating those affected.
Our thoughts, in particular, are with Detective Sergeant Nick Bailey who remains in a serious but stable condition. In responding to this incident, he exemplified the duty and courage that define our emergency services; and in which our whole nation takes the greatest pride.
Mr. Speaker, I want to pay tribute to the fortitude and calmness with which people in Salisbury have responded to these events and to thank all those who have come forward to assist the police with their investigation.
This incident has, of course, caused considerable concern across the community. Following the discovery of traces of nerve agent in Zizzi's restaurant and The Mill pub, the Chief Medical Officer issued further precautionary advice. But as Public Health England have made clear, the risk to public health is low.
Mr. Speaker, I share the impatience of this House and the country at large to bring those responsible to justice -- and to take the full range of appropriate responses against those who would act against our country in this way.
But as a nation that believes in justice and the rule of law, it is essential that we proceed in the right way -- led not by speculation but by the evidence.
That is why we have given the police the space and time to carry out their investigation properly.
Hundreds of officers have been working around the clock -- together with experts from our armed forces -- to sift and assess all the available evidence; to identify crime scenes and decontamination sites and to follow every possible lead to find those responsible.
That investigation continues and we must allow the police to continue with their work.
Mr. Speaker, this morning I chaired a meeting of the National Security Council in which we considered the information so far available. As is normal, the Council was updated on the assessment and intelligence picture, as well as the state of the investigation.
It is now clear that Mr Skripal and his daughter were poisoned with a military-grade nerve agent of a type developed by Russia.
This is part of a group of nerve agents known as 'Novichok'.
Based on the positive identification of this chemical agent by world-leading experts at the Defence Science and Technology Laboratory at Porton Down; our knowledge that Russia has previously produced this agent and would still be capable of doing so; Russia's record of conducting state-sponsored assassinations; and our assessment that Russia views some defectors as legitimate targets for assassinations; the Government has concluded that it is highly likely that Russia was responsible for the act against Sergei and Yulia Skripal.
Mr. Speaker, there are therefore only two plausible explanations for what happened in Salisbury on the 4th of March.
Either this was a direct act by the Russian state against our country.
Or the Russian government lost control of this potentially catastrophically damaging nerve agent and allowed it to get into the hands of others.
This afternoon my Rt. Hon. Friend the Foreign Secretary has summoned the Russian Ambassador to the Foreign and Commonwealth Office and asked him to explain which of these two possibilities it is -- and therefore to account for how this Russian-produced nerve agent could have been deployed in Salisbury against Mr Skripal and his daughter.
My Rt. Hon. Friend has stated to the Ambassador that the Russian Federation must immediately provide full and complete disclosure of the Novichok program to the Organization for the Prohibition of Chemical Weapons.
And he has requested the Russian government's response by the end of tomorrow.
Mr. Speaker, this action has happened against a backdrop of a well-established pattern of Russian state aggression.
Russia's illegal annexation of Crimea was the first time since the Second World War that one sovereign nation has forcibly taken territory from another in Europe.
Russia has fomented conflict in the Donbas, repeatedly violated the national airspace of several European countries, and mounted a sustained campaign of cyber espionage and disruption. This has included meddling in elections, and hacking the Danish Ministry of Defense and the Bundestag, among many others.
During his recent State of the Union address, President Putin showed video graphics of missile launches, flight trajectories and explosions, including the modeling of attacks on the United States with a series of warheads impacting in Florida.
While the extra-judicial killing of terrorists and dissidents outside Russia were given legal sanction by the Russian Parliament in 2006.
And of course Russia used radiological substances in its barbaric assault on Mr. Litvinenko. We saw promises to assist the investigation then, but they resulted in denial and obfuscation -- and the stifling of due process and the rule of law.
Mr. Speaker, following Mr. Litvinenko's death we expelled Russian diplomats, suspended security co-operation, broke off bilateral plans on visas, froze the assets of the suspects and put them on international extradition lists. And these measures remain in place.
Furthermore our commitment to collective defense and security through NATO remains as strong as ever in the face of Russian behavior.
Indeed our armed forces have a leading role in NATO's Enhanced Forward Presence with British troops leading a multinational battlegroup in Estonia.
We have led the way in securing tough sanctions against the Russian economy.
And we have at all stages worked closely with our allies and we will continue to do so.
We must now stand ready to take much more extensive measures.
Mr. Speaker, on Wednesday we will consider in detail the response from the Russian State.
Should there be no credible response, we will conclude that this action amounts to an unlawful use of force by the Russian State against the United Kingdom.
And I will come back to this House and set out the full range of measures that we will take in response.
Mr. Speaker, this attempted murder using a weapons-grade nerve agent in a British town was not just a crime against the Skripals.
It was an indiscriminate and reckless act against the United Kingdom, putting the lives of innocent civilians at risk.
And we will not tolerate such a brazen attempt to murder innocent civilians on our soil.
I commend this Statement to the House.