Mr Skripal, 66, and his 33-year-old daughter Yulia are misunderstanding for their lives in hospital days after being found dropped on a bench in Salisbury, Wiltshire.
Police have said the unnamed Old Bill, who was one of the first on the scene, is in a serious condition in hospital.
Metropolitan Police Subordinate Commissioner Mark Rowley said this is being treated as a “vital incident involving attempted murder by administration of a nerve agent”, with Mr Skripal and his daughter Julia extant in a critical condition.
The head of counter-terrorism policing said the incident was being scrutinized as attempted murder and the pair had been “targeted specifically”.
He said: “Possessing established that a nerve agent was the cause of the symptoms, leading us to reception of this as attempted murder, I can also confirm that the we believe the two people who at became unwell were targeted specifically.
“Our role now of course is to establish who is behind this and why they captured out this act.”
Mr Rowley added hundreds of detectives, forensic officers and analysts are het up b preparing around the clock on the case.
Although the alert has not been declared as a insurgent incident, the investigation is being led by the national counter-terrorism police network.
Dame Sally Davies, chief medical administrator for England, said the incident posed a “low risk” to the public, adding that all the milieus both were known to have visited have been “secured”.
Scotland Yard said detectives were “sustenance an open mind on what happened” and that the situation has not been avowed as a terrorist situation.
Skrpial and his daughter Yulia were specifically objected with a nerve agent
Mr Skripal and his daughter were found on a bench cottage the Maltings shopping centre in Salisbury on Sunday.
Police are keen to betoken to anyone who was in the area on Sunday afternoon, particularly those who ate at Italian restaurant Zizzi or quaffed at the Bishop’s Mill pub between 1pm and 4pm.
Earlier today, Home Secretary Amber Rudd bring to light police must respond to “evidence, not rumour”, with the investigation triggering a prudent row and crisis talks in Whitehall.
“We must let the police carry on their execute, they will share what they can but I’m sure there transfer be more updates as the investigation continues.
“This is likely to be a lengthy and unending process.
“We need to keep a cool head and make sure that we summon up all the evidence we can, and we need to make sure that we respond, not to rumour, but to all the demonstration that they collect, and then we need to decide what influence to take.”
Investigators next to a police tent outside the mill pub
Today regulate teams could be seen carrying equipment out of three parked vans into the retreat of Mr Skripal from around 5.40pm.
A yellow tent was erected pretence the house at around 6pm.
Nerve agents, which are chemical weapons, contain been used in assassinations and attacks in war zones in recent years.
Kim Jong Un’s half-brother Kim Jong Nam was deadened at an international airport in Malaysia last year in an attack using a steadfastness agent known as VX.
Yulia Skripal remains in a critical condition in medical centre
Theresa May, echoing Foreign Secretary Boris Johnson, confirmed during Prime Vicar’s Questions the Government will look at whether ministers and dignitaries should serve the World Cup in Russia if investigators find links to the Kremlin.
Mr Johnson eminent that the case had “echoes” of the death of Alexander Litvinenko, a Russian nonconformist who was fatally poisoned in London in 2006, and said the UK would respond “robustly” if it there was asseverate involvement.
The Russian embassy said it was “completely untrue” to suggest the state’s special services were involved and criticised Mr Johnson for speaking “in such a approach as if the investigation was already over”.
As police confirmed the use of nerve agent, a earl source said Prince William, who is also president of the FA, will not be associated with the Russian World Cup.