Russia is behind the attempted murder of an ex-spy and his daughter in Salisbury, the PM believes.

Britain gives them a week to leave and tells the UN Russia was to blame for a nerve agent attack on UK soil.

Scotland's first minister says Russia's actions cannot be tolerated as she backs the decision to expel 23 diplomats.

First minister says differences with UK government are "not insignificant, but neither are they insurmountable".

The UK will expel 23 Russian diplomats after Moscow refused to explain how a Russian-made nerve agent was used on a former spy in Salisbury, the PM says.

Theresa May said the diplomats, who have a week to leave, were identified as "undeclared intelligence officers".

She also revoked an invitation to Russia's foreign minister, and said the Royal Family would not attend the Fifa World Cup later this year.

Russia denies being involved in the attempted murder of Sergei Skripal.

The Russian Embassy said the expulsion of 23 diplomats was "unacceptable, unjustified and short-sighted".

Former spy Mr Skripal, 66, and his daughter, Yulia Skripal, 33, remain critically ill in hospital after being found slumped on a bench on 4 March.

Det Sgt Nick Bailey also fell ill responding to the incident, and is in a serious but stable condition, but is thought to be improving.

The statement has finished and we are now ending this live coverage - you can watch the statement back at the top of this page, or scroll down for key clips and text commentary. You can keep across continuing developments with BBC News here

Here are the key clips:

House of Commons
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Conservative Alec Shelbrooke earlier raised the suggestion that Jeremy Corbyn's spokesman had said there remained questions about whether Russia was behind the poisoning.

Mr Shelbrooke asked the PM if she could repeat to MPs her faith in the intelligence services "to be absolutely certain in the evidence" she has received.

Mrs May said she was "surprised and shocked at the statement that's been put out" and "it's very clear from the remarks that have been made by backbenchers from the Labour Party, that they will be equally concerned by that remark".

Here is the full text of the briefing as published by the Press Association:

Mr Corbyn's spokesman said the history of information from UK intelligence agencies is "problematic" and refused to say that the Labour leader accepted the Russian state was at fault.

He told reporters: "The government has access to information and intelligence on this matter which others don't.

"However, also there is a history in relation to weapons of mass destruction and intelligence which is problematic, to put it mildly.

"So, I think the right approach is to seek the evidence to follow international treaties, particularly in relation to prohibitive chemical weapons."

The Labour leader has been given security briefings on the incident. Asked if Mr Corbyn believed Russia was responsible for the attack, the spokesman said Mrs May continued to leave open the possibility that Russia lost control of the nerve agent.

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Former Conservative security minister John Hayes asked if local police forces were equipped and informed adequately with threats like the one that took place Salisbury.

Theresa May said the ability to bring in the capabilities of the counter terrorism police, who have regional bases, was part of the layered structure of British police.

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Plaid Cymru's Liz Saville Roberts asks the PM whether the UK is still exporting nuclear substances to Russia and asks if stopping this should be among the first sanctions imposed.

Mrs May side-steps the question and says she has been talking about the use of a nerve agent and a chemical weapon on UK soil and "the blatant flouting" of the international rules based order.

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Labour MP Stephen Kinnock offers his "full support" for the prime minister's "robust response".

He asks whether holding this year's World Cup in Russia could be seen as a "global vindication" of Russia.

He suggests exploring the possibility of postponing the event until 2019 so that it can be held in a "more appropriate" country.

Theresa May replies that it's a matter for the sporting authorities.

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Former Conservative minister Anna Soubry said "the length and breadth of this place" has supported the PM's wise words, with the "notable exception of the frontbench of the opposition and that's a shameful moment".

She asked whether, if it is proved that Russia has been trying to undermine democracy, Theresa May will take robust action.

Mrs May says she's happy to give that assurance and says the Kremlin supplies "disinformation to destabilise perceived enemies", adding that managing this "is a long term priority for the UK".

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Conservative MP Mark Francois says Theresa May's response today "had flashes of the Iron Lady about it".

He accuses Labour leader Jeremy Corbyn of being "a CND badge wearing apologist for the Russian state".

Theresa May says people "will take their own conclusions" from Mr Corbyn's comments earlier but welcomes "the positive messages of support that have come from the Labour back benches".

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Labour MP Vernon Coaker says the UK should not ban broadcasts by Russia's RT news channel.

Mr Coaker says he supports a free media and there should be a message from the UK to RT that "we're not frightened of it".

Theresa May says a decision on RT is a matter for regulator Ofcom, not for the government.

In a statement on Tuesday,, external Ofcom said:

House of Commons
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During the exchanges, it's been notable how many Labour MPs have given their support to the Prime Minister's statement - with some seeing implied criticism of their own frontbench.

Having said that, it has to be said that many of these have never been big fans of Labour leader Jeremy Corbyn.

With some English media urging that the national team be withdrawn from Russia 2018, BBC Sport takes a look at other World Cup boycotts in history.

House of Commons
Parliament

Conservative Simon Hoare asked if the government and security services were doing all they could to keep his North Dorset residents safe after the Met Police and Army were spotted in the area removing vehicles and items connected to the Salisbury incident.

Mrs May replied that the police investigation was continuing but she could not say where it will take the police.

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Labour's Ben Bradshaw tells the PM, to cheers, that "most of us on these benches fully support the measures you have set out today".

He asks that the intelligence and security services look at Putin's influence on UK universities, think-tanks, financial institutions and political parties.

Mrs May says she will "certainly look" at the suggestions he has made.