It is beyond reasonable doubt that Russia was behind the Salisbury attack, Security Minister Ben Wallace insisted as Moscow stepped up efforts to undermine the UK's case.
Russia has called for a meeting of the United Nations Security Council and foreign minister Sergey Lavrov said the UK has "legitimate questions" to answer about the nerve agent assault on Sergei Skripal and his daughter Yulia.
But Mr Wallace said that the investigation's "roads lead to Russia" as the UK sought to maintain diplomatic pressure on Moscow over the incident.
Russia called a meeting of the Organisation for the Prohibition of Chemical Weapons (OPCW) in The Hague on Wednesday to insist its experts must be involved in the testing programme and probe.
But it lost the vote after Britain told the extraordinary meeting the demand was a sign the federation was "nervous" of what the inquiries will find.
Russian officials speaking after the meeting concluded said they had presented a "common sense" case and pointed to the "lies by Tony Blair" over Iraq as they criticised the intelligence about the attack.
But Mr Wallace told BBC Radio 4's Today programme that comparisons to the flawed intelligence on weapons of mass destruction in Iraq were not valid.
"There's no missing nerve agent that no-one can find - it was used in Salisbury, we had three people seriously ill, two obviously remain in hospital in critical condition, and there is no doubt that we have found nerve agent," he said.
Labour leader Jeremy Corbyn has also raised the subject of the "flawed intelligence and dodgy dossiers" behind the Iraq invasion in his response to the Skripal case.
Mr Wallace said the Labour leader had seen more intelligence "than the average backbench MP" because he had received a Privy Council briefing on the matter - but added: "The circle of who gets to see very sensitive information is very small because if you leak it or it gets out, people's lives are put at risk."
Foreign Secretary Boris Johnson - who has come under fire over his handling of the incident - has accused Mr Corbyn of siding with the "Russian spin machine".
Moscow has asked for an open session of the UN Security Council to be held on Thursday at 8pm UK time.
Tension between Moscow and London has risen after the head of the Porton Down military research facility said scientists had not verified Russia as the source of the substance used in the attack on the Skripals.
Vladimir Putin seized on the comments from the chief executive of the Government's Defence Science and Technology Laboratory (DSTL), Gary Aitkenhead, as he accused the UK of launching an "anti-Russian campaign".
But UK security services have a high degree of confidence that they have pinpointed the location of the Russian laboratory that manufactured the nerve agent used in the attack, according to The Times.
A Whitehall source told the newspaper: "We knew pretty much by the time of the first Cobra (the emergency co-ordination briefing that took place the same week) that it was overwhelmingly likely to come from Russia."
The Foreign Secretary, who has faced claims he exaggerated the evidence against Moscow, said countries around the world "continue to share our assessment" about the nerve agent attack.
He said: "The international community has yet again seen through these tactics and robustly defeated Russia's attempts today to derail the proper international process."
In the latest sign of the international storm created by the Salisbury attack, expelled US diplomats appeared to be leaving Moscow.
Russia last week ordered 60 American diplomats to leave the country by Thursday in retaliation for the United States expelling the same number of Russians.