Sergei Skripal and his daughter was poisoned with Novichok of a “high purity,” the Organisation for the Protection of Chemical Weapons said on Thursday.

The confirmation of the chemical’s identity bolsters Britain’s case that Russia was behind the attack last month.

Britain accused Russia of manufacturing the nerve agent used in the attack, and has reportedly named a secretive military lab in southwestern Russia as the source.

While the OPCW did not explicitly name the poison as Novichok, it confirmed the UK’s analysis which does.

The OPCW said: "The results of analysis by the OPCW designated laboratories of environmental and biomedical samples collected by the OPCW team confirm the findings of the United Kingdom relating to the identity of the toxic chemical that was used in Salisbury and severely injured three people."

Boris Johnson said on Thursday: "There can be no doubt what was used and there remains no alternative explanation about who was responsible - only Russia has the means, motive and record."

The Foreign Secretary added that Britain had called a meeting with the OPCW next Wednesday to "discuss next steps."

Russia has repeatedly denied its involvement in the attack and even pushed multiple contradictory theories to claim so.

The OPCW collected samples at the site of the attack in Salisbury, as well as blood samples from the Skripals and Sergeant Nick Bailey, who was poisoned while responding to the attack, last month.

Russia's proposal to join the OPCW investigation was shot down last week. Aleksander Shulgin, Moscow's ambassador to the OPCW, said before losing the vote that the Kremlin would reject the outcome of the report.

Read Boris Johnson's statement:

"There can be no doubt what was used and there remains no alternative explanation about who was responsible - only Russia has the means, motive and record.

"We invited the OPCW to test these samples to ensure strict adherence to international chemical weapons protocols. We have never doubted the analysis of our Scientists at Porton Down.

"In the interest of transparency, and because unlike the Russians we have nothing to hide, we have asked the OPCW to publish the executive summary for all to see and to circulate the full report to all state parties of the OPCW, including Russia."