Britain has placed sanctions on Russia’s chemical warfare unit and its commander for dropping toxic First World War choking gas over battlefields in Ukraine.

David Lammy, the Foreign Secretary, said that Russia was “riding roughshod” over international laws by deploying banned toxic agents.

“Russia’s cruel and inhumane tactics on the battlefield are abhorrent and I will use the full arsenal of powers at my disposal to combat Russia’s malign activity,” he said.

In May, the US accused Russia of dropping chloropicrin on Ukrainian soldiers “to dislodge them from fortified positions”.

Chloropicrin, which is an oily substance that was widely used on trenches during the First World War, causes irritation to the eyes and skin and can induce vomiting and diarrhoea.

The chemical agent is banned under the 1997 Chemical Weapons Convention, which Russia has signed. The US has also accused Russia of dropping crowd-control tear gas on Ukrainian soldiers.

In its statement on Tuesday, the Foreign Office said that Lt Gen Igor Kirillov, the head of Russia’s Radiological Chemical and Biological Defence unit since 2017, was “a significant Kremlin mouthpiece” used to spread lies around chemical weapons to “mask Russia’s shameful and dangerous behaviour”.