Theresa May is to chair a National Security Council meeting to discuss who was behind the nerve agent attack on an ex-Russian spy and his daughter.
The latest intelligence will be presented to the committee of ministers and intelligence and military chiefs.
Sergei and Yulia Skripal remain in a critical but stable condition.
Foreign affairs committee chairman Tom Tugendhat said evidence was mounting against Russia, which has denied involvement in the attack in Salisbury.
“We are expecting to see the prime minister make an announcement soon,” he told BBC Radio 4’s Today programme.
“And, frankly, I would be surprised if she (Theresa May) did not point the finger at the Kremlin.”
The BBC’s home affairs correspondent Daniel Sandford said the security committee will consider whether there is enough evidence to take action, and whether it is the right time to do so.
Lord Ricketts, a former national security advisor, told BBC Radio 4’s Today programme he had “little doubt that this had come from Russia”.
“The really difficult judgement is who authorised it and why – was it some sort of rogue element or was it centrally authorised, I suppose that does have some impact on the kind of reactions that we need,” he said.
The government should take “pretty firm action”, he said, once a conclusion on responsibility was reached.
“We need to make the guys in the Kremlin sit up and take notice,” he said, suggesting that action could include the expulsion of diplomats.
Mr Skripal, a retired Russian military intelligence officer, was convicted by the Russian government of passing secrets to MI6 in 2004, but given refuge in the UK in 2010 as part of a “spy swap”.
On Sunday, up to 500 Salisbury pub-goers and diners were told to wash their possessions as a precaution.
Trace amounts of the substance used to poison the pair were found on and around a table where they had eaten in Zizzi on 4 March. The table has since been destroyed.
As well as in Zizzi’s restaurant, traces of the nerve agent were also found at the Mill pub in Salisbury.
Prof Dame Sally Davies, the chief medical officer for England, said the risk of harm to fellow diners was “low”.
The advice to wash possessions applies to anyone in either venue between 13:30 GMT on Sunday 4 March to closing time on Monday. People have been advised:
- Clothes should be washed, ideally in a washing machine
- Clothes which cannot be washed, for example if they need dry cleaning, should be double bagged in plastic until further notice
- Mobile phones, handbags and other electronic items should be wiped with baby wipes, which should be bagged in plastic and put in the bin
- Other items such as jewellery and glasses should be washed with warm water and detergent
- Hands should be washed after the handling of any items suspected of being contaminated
Dame Sally said the advice was a “belt and braces” measure, adding: “I am confident none of these customers or staff will have suffered harm.”
Some Salisbury residents were concerned the advice was not given sooner.
Steve Cooper, who was at the Mill pub with his wife on 4 March, told the BBC he was outraged.
He said he would now wash his shoes, watch and phone but feared using baby wipes would not get rid of a nerve agent.
“I’d like to know what are the long-term implications to me and my wife,” he said.
Salisbury City Council leader Matthew Dean told BBC Radio 4’s Today programme that he believed the advice to wash clothes was timely 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 said.
Mr Skripal, 66, and his daughter Yulia, 33, were found slumped on a bench in the city.
Det Sgt Nick Bailey, who fell ill attending the pair, remains seriously ill in hospital but has been talking to his family.
The pub and restaurant are two of five sites in Salisbury focused on by investigators.
Mr Skripal’s home and the cemetery where Mr Skripal’s wife and son are buried are also being examined.
At a press conference on Sunday, Chief Constable Kier Pritchard of Wiltshire Police said he was “unable to clarify” how long those crime scenes would remain closed to the public.
Military personnel continued to assist police over the weekend, and removed vehicles including an ambulance.
More than 250 counter terrorism police are involved in the investigation, which so far has yielded 200 pieces of evidence and more than 240 witnesses.
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