The Kremlin will be blamed for murdering Alexander Litvinenko in London, and Vladimir Putin will even be named in a public inquiry’s report into the former Russian spy's poisoning with a radioactive substance, according to reports.
The conclusion that agents of the Russian state were responsible for the dissident’s death comes at a time when the UK is working with Moscow to deal with Isis in Syria and amid tensions over Russian troops in Ukraine.
On Wednesday, Defence Secretary Michael Fallon said that the UK was going to send more military personnel to Nato countries in eastern Europe because of the potential threat posed by “Russian aggression”.
A Government source told The Daily Telegraph that the public inquiry’s report would show the Russian government - but perhaps not President Vladimir Putin himself - wanted Mr Litvinenko dead.
“There will be a clear line of command. It will be very clear that the orders came from the Kremlin, that it was ordered by the government,” the source said.
Another insider warned: “The findings will place the UK in a difficult position given our relations with Russia in current international events.”
The Times reports that Mr Putin will be named in the report, but ithe extent of his alleged involvement in the killing will remain unclear.
It is expected the British Government will now make fresh calls for the two main suspects, Andrey Lugovoy and Dmitry Kovtun, to be extradited to the UK.
Mr Litvinenko, 43, drank a cup of green tea containing Polonium-210, which is highly radioactive, at the Millennium Hotel, London, in November 2006. He died three weeks later. He was a prominent critic of Mr Putin and he had been working with MI6.
Sir Robert Owen, a retired judge, chaired the public inquiry last year and his report is due to be published on Thursday.
Party leader Tim Farron said: “If the Russian state is found to be behind this, we cannot just put out a few strong words drafted by a diplomat in the Foreign Office, we must act.
"The brutal murder of Litvinenko in 2006 exposed the cruel reality of a Russian state which continues to the cold-war pursuits of espionage and extra-judicial killing.
“By poisoning one of their own on British soil, the Russian government completely disregarded the rule of law both within the UK and internationally.”
Mr Fallon and Foreign Secretary Philip Hammond met their counterparts from Poland at Edinburgh Castle on Wednesday for discussions around defence and EU reform.
“This year we are confronting dangers that are growing in scope, in complexity and diversity, from the Islamist evil that is causing chaos and death in Syria and Iraq to the Russian aggression that we have seen in the Crimea and in Ukraine destabilising our eastern border,” Mr Fallon said.