"Russia is not guilty," said Foreign Minister Sergei Lavrov of the attack on Sergei Skripal and his daughter in Salisbury on March 4.
The United States, NATO and the European Union have all backed Britain in the deepening diplomatic crisis.
Lavrov said Russia was "ready to cooperate", but complained Britain had rejected its requests for "access" to the nerve agent samples.
German Foreign Minister Sigmar Gabriel also said on Tuesday that any Russian connection to the poisoning in Britain of a former double agent would be a “very serious matter.”
“We stand in solidarity on this issue with our British friends and are in close contact with the British government,” Gabriel said in a statement after speaking with his counterpart Boris Johnson.
“It is clear, the perpetrators must be brought to justice. If it should be confirmed that Russia is behind it, it would be a very serious matter.”
Meanwhile, British police investigating the poisoning will not at this stage name any potential suspects as their enquiries continue, a senior police officer said on Tuesday.
“At this stage, we are not declaring a person of interest or a suspect at this time,” Neil Basu, Senior National Co-ordinator for counter terrorism policing, told reporters.
Police say investigation into nerve agent attack on ex-Russian spy will continue for many weeks.
However, Moscow has called Britain’s accusations of its involvement in the poisoning of a former double agent an attempt to “discredit” Russia and vowed to retaliate against any sanctions.
“The incident is yet another dirty attempt by British authorities to discredit Russia,” the Russian foreign ministry said in a statement, adding that threats of sanctions “will not be left without a response.”