Russia has failed in its "ludicrous" bid for a joint UK/Russian investigation into the Salisbury attack, Boris Johnson has said.
Moscow called a meeting of the Organisation for the Prohibition of Chemical Weapons (OPCW) in The Hague 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 Moscow was "nervous" of what the inquiries will find.
Mr Johnson said Russia's goal was to "obscure the truth and confuse the public".
The Foreign Secretary, who has faced claims he has exaggerated the evidence against Moscow, said countries around the world "continue to share our assessment" about the nerve-agent attack.
He said: "The purpose of Russia's ludicrous proposal at The Hague was clear - to undermine the independent, impartial work of the international chemical weapons watchdog.
"Russia has had one goal in mind since the attempted murders on UK soil through the use of a military-grade chemical weapon - to obscure the truth and confuse the public.
"The international community has yet again seen through these tactics and robustly defeated Russia's attempts today to derail the proper international process.
"It shows that many countries around the world continue to share our assessment of what happened in Salisbury and are determined to stand up to Russia's behaviour."
In a vote at OPCW, six of the 41 members backed Russia while 15 voted against, 17 abstained, two were absent, and one was not entitled to vote.
Nick Heath, deputy British ambassador to The Hague, said Russia had failed again in its attempts to "frustrate the process of justice".
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.
Moscow has called for an emergency session of the UN Security Council on Thursday to discuss the case.
Only six of the 41 OPCW members voted in favour of the Russian draft decision proposing the joint UK/Russian investigation. 15 voted against, including the UK, 17 abstained, 2 were absent, and one was not entitled to vote.
UK ambassador John Foggo accused Russia of showing "disdain" for the independence of the international body, which is conducting tests on samples of the nerve agent used in the March 4 attack on ex-spy Sergei Skripal and his daughter Yulia.
He told the meeting: "The work of the Technical Secretariat must remain impartial.
"Russia's refusal to accept the results of the OPCW's investigation unless Russian experts participate in it suggests that Russia is opposed to the independence and impartiality of the Technical Secretariat and is nervous about what the results will show."
Mr Foggo said that Russia's statements displayed a "wilful ignorance" of the Chemical Weapons Convention and "disdain for the independence and competence" of the OPCW's Technical Secretariat.
The UK was backed by the European Union, which reaffirmed its support for Britain's demand for answers from Russia on how the Novichok agent which it developed came to be used in Salisbury.
Speaking on behalf of the EU, Bulgarian ambassador Krassimir Kostov said: "We have full confidence in the UK investigation and laud UK's collaboration with the OPCW Technical Secretariat, in full compliance with the convention."
Tension between Moscow and London has risen a notch 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".
Russia has flatly denied UK claims that it was to blame for the March 4 attack, with foreign intelligence service director Sergei Naryshkin even claiming it was staged by the UK and US as a "provocation".
Mr Naryshkin told a global security conference in Moscow: "Even as far as the Skripal case goes - which is a grotesque provocation rudely staged by the British and US intelligence agencies - some European countries are in no hurry to follow London and Washington, preferring to sort the situation out."