Foreign secretary Boris Johnson has warned that England may pull members out of their football delegation for the forthcoming FIFA World Cup in Russia in the wake of the mysterious collapse of former spy Sergei Skripal.

Johnson warned that the England team, who are meant to play in Russia this summer, could be pulled if Moscow were shown to be behind the attack.

In 2004, Skripal was convicted by Russia of "high treason in the form of espionage" for betraying dozens of spies to British intelligence. He was released in 2010 as part of a spy exchange program.

He was found along with his daughter, Yulia, collapsed on a bench in Salisbury, Wiltshire, on Sunday afternoon (4 March). The pair both remain in a critical condition in intensive care.

Speaking from the House of Commons on Tuesday, Johnson issued a stark warning to Russia: "We don't know exactly what has taken place in Salisbury, but if it's as bad as it looks, it is another crime in the litany of crimes that we can lay at Russia's door.

"It is clear that Russia, I'm afraid, is now in many respects a malign and disruptive force, and the UK is in the lead across the world in trying to counteract that activity."

He added that if a connection to Russia was found to the attack "I think it will be difficult to see how UK representation at the World Cup in Russia can go ahead."

Aides to Johnson have stressed that members from groups such as the FA would be pulled rather than the England team themselves.

Russia has so far denied any involvement in the incident which is now being investigated by the counter-terrorism police.

Johnson also compared the incident with the death of Alexander Litvinenko in 2006. The Russian dissident and former intelligence officer died more than ten years ago in London after he drank tea laced with a radioactive substance.