Senior figures from the global chemical weapons watchdog have flatly rejected Russian claims that the watchdog’s laboratories had found a western military chemical agent in the poison that incapacitated the Russian double agent Sergei Skripal.

In a weekend claim widely picked up on social media, the Russian foreign minister, Sergei Lavrov, said that a Swiss laboratory used by the Organisation for the Prohibition of Chemical Weapons had discovered traces in the sample of the nerve agent BZ and its precursors. The nerve agent is possessed by Nato countries, but not Russia.

The Russian embassy in London said it was “highly likely” that BZ had therefore been used in Salisbury, adding that the OPCW and the British had questions to answer.

But at a meeting of the OPCW executive in The Hague, the Russian claim was refuted by OPCW officials, who said explained that BZ had been used in the control sample, not the sample itself. It is also a breach of OPCW procedures to identify a laboratory involved in a test.

The UK said Russia had been caught out in an attempt to mislead the international community, adding the OPCW report showed the world was facing “a clear case of a new family of toxic chemicals intended to kill”.

The west also bluntly criticised Russia for generally endangering the integrity and respect for OPCW scientists in a bid to clear itself of the allegation that it was behind the use of a nerve agent that poisoned Skripal and his daughter, Yulia, in Salisbury last month.

The Swiss delegation described Lavrov’s behaviour as incomprehensible and totally unacceptable. Sabine Nölke, the Canadian envoy to the OPCW, accused Russia of either “a craven attempt to mislead the international community”, or a breach of the OPCW’s confidentiality procedures. The EU described the Russian behaviour as malign.

The OPCW meeting had been called by the UK to discuss an OPCW technical report completed last week confirming that the UK’s Porton Down laboratories had correctly identified the nerve agent as novichok. The UK continued to assert that only Russia had the motive, technical ability and operational experience to produce the agent.

The OPCW is not empowered to identify the source of the nerve agent, but Russian media claimed the OPCW’s refusal to identify Russia as a source was a vindication for the Kremlin.

Referring to Lavrov’s claims about the discovery of BZ, Marc-Michael Blum, the head of the OPCW laboratory, told the meeting: “The labs were able to confirm the identity of the chemical by applying existing, well-established procedures. There was no other chemical that was identified by the labs. The precursor of BZ that is referred to in the public statements, commonly known as 3Q, was contained in the control sample prepared by the OPCW lab in accordance with the existing quality control procedures. Otherwise it has nothing to do with the samples collected by the OPCW team in Salisbury.”

The OPCW director general, Ahmet Üzümcü, also pushed back against recent Russian claims of bias, saying its scientists had been able “to collect both biomedical and environmental samples under full chain of custody and also splits of earlier samples taken by the British authorities for comparative purposes. The OPCW analysis clearly confirms the findings of the United Kingdom relating to the identity of the toxic chemical used in Salisbury that severely injured three people.”

In his presentation, the UK OPCW envoy pointed out that the OPCW noted that the chemical was of high purity, indicating that the chemical was not volatile and would degrade slowly. “All this is cause for grave concern as we now face a clear case of a new family of toxic chemicals intended to kill,” he said.

The EU also demanded answers from Russia about its responsibilities for a “shocking and reprehensible act”. In its statement, it said: “We regret that we continue to witness persistent and malign Russian attempts to undermine the credibility of the OPCW secretariat and technical report. All this is aimed at hampering and obscuring the investigation in a manner that damages the credibility of the chemical weapons convention.”

Russia, for its part, suggested that the Skripal’s body samples might have been manipulated by British medical experts while in an induced coma.