Police and prosecutors said there is sufficient evidence to charge Alexander Petrov and Ruslan Boshirov with conspiring to murder Sergei Skripal and attempting to murder the ex-Russian spy, his daughter Yulia and Wiltshire Police detective sergeant Nick Bailey.
Metropolitan Police Assistant Commissioner Neil Basu said the two suspects are aged around 40 and it is likely they were travelling under aliases and Petrov and Boshirov are not their real names.
Prosecutors will not be applying to Russia for the extradition of the two men, but a European Arrest Warrant has been obtained.
Mr Skripal and his daughter Yulia were poisoned in March by the nerve agent Novichok.
Detectives believe the front door of Mr Skripal’s Salisbury home was contaminated with the military-grade substance on Sunday March 4.
Mr Basu said CCTV shows the two suspects in the vicinity of the property on that date.
Hours later, the men left the UK on a flight from Heathrow to Moscow - two days after they had arrived at Gatwick.
Mr Basu said: “We have no evidence that they re-entered the UK after that date.”
The announcement on Wednesday relates to the first incident, but Mr Basu confirmed that officers have now linked the attack on the Skripals to events in Amesbury less than four months later.
In the second incident, Dawn Sturgess, 44, and her partner Charlie Rowley, 48, were exposed to the same nerve agent used in Salisbury. Ms Sturgess died in hospital in July, just over a week after the pair fell ill.
Mr Basu said: “We do not believe Dawn and Charlie were deliberately targeted, but became victims as a result of the recklessness in which such a toxic nerve agent was disposed of.
“We know that Novichok was applied to the Skripals’ front door in an area that is accessible to the public, which also endangered the lives of members of the public and emergency service responders.”
Police released an image of a perfume bottle recovered from Mr Rowley’s home which is thought to have contained Novichok.
He said police continue to liaise with the CPS regarding the poisoning of Ms Sturgess and Mr Rowley.