Britain's Foreign Secretary Boris Johnson has accused Opposotion Leader Jeremy Corbyn of "siding with the Russian spin machine" over the poisoning of a spy in Salisbury.
Corbyn said that Johnson has "serious questions" to answer after saying in an interview a fortnight ago that he had been told by Porton Down scientists that the nerve agent used in the poisoning was made in Russia.
Yesterday scientists from Porton Down said that while they had established that the poison used in Salisbury was the Russian-developed nerve agent Novichok, they could not determine precisely where it was made.
Vladimir Putin, the Russian President, seized on the interview, and the Russian Embassy in the UK subsequently highlighted a deleted Foreign Office tweet claiming scientists had concluded the agent was "produced in Russia".
Corbyn said that Johnson had "egg on his face" and had "completely exceeded the information" he had been given.
Johnson said: "It is lamentable that Jeremy Corbyn is now playing Russia's game of trying to discredit the UK over [the] Salisbury attack.
"Twenty-eight other countries have been so convinced by [the] UK case they have expelled Russians. In contrast, Jeremy Corbyn chooses to side with the Russian spin machine."
Johnson and the Government have made it clear that Russia said that the analysis of the agent was only "one part of the intelligence picture", highlighting Russian research into delivering nerve agents to assassinate targets and record of "state-sponsored assassinations".
Earlier Diane Abbott, Labour's shadow home secretary, said that the statement from Porton Down had raised questions about the Government's approach, and that claimed the Opposition Leader should be given credit for demanding more evidence before allocating blame.
"It doesn't surprise me Porton Down is saying this because the security services were always very cautious in what they said," Abbott told BBC Radio 4's Today programme.
"What surprised me was that so many were willing to rush into the media and say it was unequivocally Putin. That's not necessarily what we were told."
It came as Britain called Russia's demand for a joint intervention into the Salisbury poisoning "perverse" at a meeting of the Organisation for the Prohibition of Chemical Weapons in the Hague.
Britain's representative at the meeting said: " We will not agree to Russia's demand to conduct a joint investigation into the attack in Salisbury because the UK – supported by many other countries – has assessed that it is highly likely that the Russian state is responsible for this attack, and that there is no plausible alternative explanation.
"There is no requirement in the Chemical Weapons Convention, for a victim to engage the likely perpetrator in a joint investigation. To do so would be perverse."
Russia recieved the backing of 14 nations at the meeting including Cuba, Pakistan, Iran, Nicaragua, Russia, Venezuela, Syria and Belarus.