Russia has been warned of a “dramatic increased response” from the West if Vladimir Putin resorts to deploying chemical weapons in Ukraine.
As Boris Johnson and western allies raised concerns over the potential use of the banned weapons, the technology minister Chris Philp urged the Kremlin “not to cross that line”.
Last night the prime minister claimed the “cynical, barbaric” regime in Moscow had a “fake story ready to go”, with baseless claims of its opponents storing chemical weapons.
“The stuff which you are hearing about chemical weapons is straight of the Russian playbook,” Mr Johnson told Sky News presenter Beth Rigby.
Speaking to Times Radio, Mr Philp said the use of chemical weapons, “especially in an invasion where there are a very large number of civilians, would be an outrage against humanity”.
“I would say to anybody in Russian thinking about this: do not cross that line, do not inflict any more misery and suffering on the Ukrainian people”.
He added: “They’ve already been shooting civilians who are fleeing down humanitarian escape corridors, they’ve been bombing and shelling hospitals including a children’s maternity hospital, do not go any further in inflicting misery on the Ukrainian people.
“It will trigger an increased response from the West, there’s a dramatic increased response, there’s no question about that.
“I’m not going to speculate about the form that’s going to take or pre-empt it, but that’s a line the Russian government should not cross”.
His comments echo those of the armed forces minister, James Heappey, who warned the Russia president needed “to be very clear that when other countries have used chemical weapons it has caused an international response”.
During a trip to Washington on Thursday, the foreign secretary Liz Truss also said the government was “very concerned” about the potential use of chemical weapons while the White House press secretary said the world should be “on the lookout” for the Russian use of chemical and biological weaponry.
Last night, however, Mr Johnson again dismissed calls for a no-fly zone over Ukraine, amid fears such action could bring the UK and its Nato allies into a direct conflict with Russian forces.
Referring to the Kremlin’s bombing of a maternity hospital in the Ukrainian port city of Mariupol, the prime minister said it showed that Putin is prepared to abandon “all norms of civilised behaviour”.
He added: “The difficulty is that there is a line beyond which, quite frankly, the UK and Nato would be deemed to be in conflict — direct conflict — with Russia.
“It’s agonising. It’s absolutely agonising. And I’ve had this conversation at least a couple of times now with Volodymyr, but I think the difficulty is that it will require me to order RAF jets, UK pilots into the air with a mission to shoot down Russian fast jets. I think we’ve got to be realistic... there’s a line that is very difficult to cross.”
