Britain's ambassador to the Organization for the Prohibition of Chemical Weapons said on Tuesday Russia had failed to declare its full stockpile of nerve agents to the international body.
Peter Wilson told reporters that Russia, which says it destroyed all its chemical weapons under OPCW supervision last year, has in fact "failed for many years" to fully disclose its chemical weapons program.
Wilson repeated assertions by the British government that Russia was "implicated" in the attack last week on a former spy in Britain, and demanded that Moscow now declare its undisclosed program.
The British government says the former spy and his daughter were attacked in Salisbury with Novichok, a nerve agent first developed by the Soviet Union in the 70s and 80s.
Speaking to reporters after a meeting of the OPCW's governing council, Wilson said Russia will also have to tell the body how the substance managed to get to Britain from Russia.
In an address to the OPCW earlier, Wilson said the only possible explanations were that Russia had failed to keep control over its material, or had used toxic agents intentionally in the attack - the same reasoning set out by British Prime Minister Theresa May in parliament on Monday.
Earlier Tuesday, OPCW Director General Ahmet Uzumcu condemned the attack. It is not yet clear whether the organisation, set up to prevent the use of chemical weapons and oversee the destruction of existing stockpiles, would investigate or take any other action.
Trump says will talk to May about nerve agent attack
US President Donald Trump said he planned to talk to British Prime Minister Theresa May later on Tuesday about the nerve agent attack in Salisbury, England, that struck down a former Russian double agent who passed secrets to British intelligence."It sounds to me that it would be Russia based on all the evidence they have," Trump told reporters. "As soon as we get the facts straight, if we agree with them, we will condemn Russia or whoever it may be."