British counter-terror police said Sergeev met the two agents who then travelled to Salisbury “on more than one occasion” over the weekend of the attack, but that no traces of novichok were found at his hotel.
A third Russian spy has been charged with involvement in the 2018 Salisbury novichok attack.
Denis Sergeev, who travelled to the UK under the alias Sergey Fedotov, is believed to have commanded the two GRU agents who carried out the poisoning from London.
He flew from Moscow to Heathrow Airport on 2 March 2018, arriving around four hours before his colleagues, and stayed at a hotel in Paddington for two nights.
Sergeev, aged around 50, flew back to Moscow from Heathrow at 1.45pm on 4 March, less than two hours after the nerve agent was applied to Sergei Skripal’s door.
The Crown Prosecution Service (CPS) has authorised the same charges against him as the two previous suspects, including the attempted murder of Mr Skripal and his daughter Yulia, the grievous bodily harm of police officer Nick Bailey and the use of novichok as a chemical weapon.
The Senior National Coordinator for Counter Terrorism Policing said Sergeev “operated as a team” with Alexander Petrov, alias Alexander Mishkin, and Ruslan Boshirov, alias Anatoliy Chepiga.
Metropolitan Police Deputy Assistant Commissioner Dean Haydon, told a press conference: “They came here separately in two groups, Petrov and Boshirov together, Fedotov by himself, met, and without a doubt they’ve operated as a small team with a view to deploying novichok to kill people in this country.
“There is other intelligence that suggests they’ve been here before, but in other countries as well working as a threesome and likely with others … in relation to similar attacks.”
British police are working with their counterparts in Bulgaria and the Czech Republic, in relation to attacks linked to the same suspects. Invetigators said there was no evidence that they have been involved in previous attacks in the UK.
The charges announced on Tuesday do not cover the death of Dawn Sturgess, a 44-year-old mother, who died in July 2018 after her boyfriend found a counterfeit perfume bottle containing the nerve agent.
Charlie Rowley gave Ms Sturgess what he believed to be a present in Amesbury, near Salisbury, not knowing it contained enough novichok to kill “thousands of people”, police said.
He survived being poisoned after quickly washing the substance off, but Ms Sturgess died days after applying it to her skin in the belief it was perfume.
Mr Haydon said the investigation into how Mr Rowley found the bottle in June 2018, and where it had been following the Skripal attack almost four months earlier, was still ongoing.
“ There are still parts of the picture we have not been able to piece together,” he added. “We remain as determined as ever to bring those responsible for Dawn’s murder and Charlie’s poisoning to justice.”
The CPS is not applying to Russia for an extradition warrant because the country’s constitution does not permit the extradition of its own nationals.
Instead, Interpol red notices have been issued meaning the suspects can be arrested if they leave Russia – where all three men are believed to remain.
Mr Haydon said British authorities had seen “very little cooperation from Russia” since 2018, or in previous cases such as the murder of Alexander Litvinenko.
The European Court of Human Rights ruled on Tuesday that Russia was responsible for the 2006 killing of the ex-KGB officer Litvinenko who died an agonising death after he was poisoned in London with Polonium 210.
Mr Haydon added: “The Foreign Office will be talking on diplomatic channels to Russia but from the police investigation side, our due process is to seek arrest warrants and circulate those through Interpol.