Theresa May will update MPs on the investigation into the nerve agent attack on Russian spy Sergei Skripal and his daughter amid speculation the Kremlin was behind the poisoning.
The Prime Minister was briefed by police and intelligence chiefs on the latest developments in the case at a meeting of the National Security Council (NSC) in Downing Street.
Her appearance in Parliament on Monday afternoon comes after the chairman of the Commons Foreign Affairs Committee said the incident looked like a "state-sponsored" murder attempt.
Tom Tugendhat said he would be surprised if Mrs May did not blame the Kremlin for the poisoning of Sergei Skripal and his daughter Yulia.
Ahead of the Prime Minister's statement, Downing Street said "if we get to a position when we are able to attribute this attack then we will do so".
The Kremlin has denied the involvement of the Russian government in the nerve agent attack on the Skripals.
But senior Tory MP Mr Tugendhat told BBC Radio 4's Today programme the Salisbury incident was "looking awfully like it was state-sponsored attempted murder".
Mr Tugendhat added that he would be surprised if Mrs May "did not point the finger at the Kremlin".
In response to a request for comment from the Press Association, Vladimir Putin's press secretary Dmitry Peskov said: "We consider inappropriate any mention of the Russian government in the context of what happened to Sergei Skripal.
"We have nothing to do with the story."
Home Secretary Amber Rudd said she would not yet point the finger of blame for the "outrageous and horrific" attack in the Wiltshire city on March 4 but she directly accused Moscow of trying to provoke Britain into a slanging match.
Last week, as Mr Skripal, 66, and his daughter Yulia, 33, lay critically ill in hospital, a Russian state TV presenter jibed that "traitors" were not safe in England, where "people get hanged, poisoned, they die in helicopter crashes and fall out of windows in industrial quantities".
Yury Filatov, a diplomat, said the UK was "very dangerous for certain types of people who are under the jurisdiction of the British government".
Ms Rudd said: "I'm not going to enter into a kind of great big tit-for-tat with them, which is what they are longing I'm sure for us to do.
"Because when attribution comes we have to be absolutely cool-headed about it. Other people can carry on making their comments. I think that the general public are wise enough to take a dim view of that kind of childish joshing."
She said that the NSC would consider strong measures if "a hostile state" were found guilty of the poisoning.
"If you can attribute this, then you would have to have a response. And when you attribute it, you need to have a plan," she said.
Any sanctions would take into account "other diplomatic relations, other equities that people have in different countries and the response to the response".
Reports at the weekend suggested that the Prime Minister was under pressure from senior ministers including Foreign Secretary Boris Johnson and Defence Secretary Gavin Williamson to take a tougher line on Russia.
But Downing Street said it did not recognise reports of a Cabinet split and said blame would be apportioned only if the evidence was clear.
The Prime Minister's official spokesman said: "You have seen words from the PM, Home Secretary and Foreign Secretary and they are very clear that this is an ongoing investigation, that it is important that we allow the police to get on with their work, that we gather all the evidence and if we get to a position when we are able to attribute this attack then we will do so and the Government will deliver an appropriate response."
The meeting comes as the former spy and his daughter remain critically ill in hospital eight days after they were found collapsed on a bench in the Wiltshire city.
Detective Sergeant Nick Bailey is in a serious but stable condition in the Salisbury District Hospital, where he is said to be conscious and talking.
On Sunday, hundreds of diners and pub-goers were urged to wash clothes and other items a week after potentially coming into contact with the nerve agent.
The "precautionary advice" was issued after traces of the substance were found in The Mill pub and the nearby Zizzi restaurant, in Salisbury.
The Tory leader of Salisbury City Council, Matthew Dean, insisted advice given to members of the public to wash their clothes if they had been to the venues Mr Skripal had visited had been issued quickly enough.
"I think what I am very confident about is that consistently the advice has been that this is a very, very precautionary approach and that they are advising that people wash their clothes because they don't want people to come into prolonged contact," he told the BBC.
Downing Street also backed the handling of the situation by chief medical officer Dame Sally Davies and Public Health England.
The PM's spokesman said: "She explained that they only received the latest piece of scientific analysis on Saturday and they put in place an information programme making sure they had a website ready so that the public were able to access all the information they needed early on Sunday morning."