U.K. Foreign Secretary Boris Johnson | Attila Kisbenedek/AFP via Getty Images Boris Johnson warns Russia over ‘acts of war’ The British foreign secretary promised the UK government would respond ‘appropriately and robustly’ if Russia was behind the apparent poisoning of a spy.

LONDON — U.K. Foreign Secretary Boris Johnson on Tuesday denounced Russia as an increasingly “malign” influence in global affairs after the discovery of a Russian double agent slumped unconscious on a bench in Salisbury, England, having apparently been poisoned.

Speaking in the House of Commons, Johnson said the incident had “echoes” of Russia’s state-sanctioned murder of another former agent living in Britain, Alexander Litvinenko, and warned such violence needed to be reclassified as “acts of war” to deter further attempts on the lives of people living in the U.K.

“I increasingly think we need to classify them as acts of war,” Johnson told MPs. “We need to elaborate a new doctrine of response and a new doctrine of deterrence as well.”

The stark warning came as Johnson called into question the England football team’s participation in this summer’s World Cup in Russia.

Johnson said while he did not want to pre-judge the results of the inquiry into the incident, which has left 66-year-old Sergei Skripal and his daughter Yulia in intensive care, should evidence emerge that it was an attack directed by Moscow, involvement in the upcoming tournament would be hard to justify.

“It would be very difficult to imagine how U.K. representation at that event could go ahead in the usual way and we would have to consider that,” Johnson said.

A spokesman for the foreign secretary later clarified this remark, insisting Johnson did not mean the England squad would boycott the tournament, but rather dignitaries and officials who attend.

Johnson was responding to an urgent parliamentary question put forward by the chairman of the foreign affairs select committee Tom Tugendhat who said Moscow was conducting “a form of soft war … against the West.”

Johnson said Russia was now a “malign and disruptive force” in global affairs and needed to be sanctioned as a result.

In his opening statement, the foreign secretary said: “Should evidence emerge that implies state responsibility then her majesty’s government will respond appropriately and robustly.”

“I know members will have their suspicions. If those suspicions prove to be well founded this government will take whatever measures it deems necessary. No attempt to take innocent life on U.K. soil will go unsanctioned or unpunished.”

There were calls from across the House of Commons to take a stronger line against Moscow.

Labour MP Chris Bryant said the U.K. needed to “make it clear to Russia you cannot kill people on our streets.”

The debate in the House of Commons came as the Daily Telegraph reported that Skripal was still providing help to MI6 while exiled in the U.K. after a spy swap.

U.K. police are investigating what "unknown substance" harmed the pair.

On Tuesday Russia insisted it had "no information" on what could have led to the incident.