Jeremy Corbyn last night refused to say whether he would defend a Nato ally if it were invaded by Russia.

The Labour leader was asked multiple times at a leadership debate in Birmingham if he would uphold the Nato principle of "collective defence" where an attack against one member is considered an attack against all.

But he refused to give concrete assurance that he would do so were he prime minister.

Instead he said: “I would want to avoid us getting involved military, by building up democratic relationships."

The Labour leader repeatedly stressed the importance of improving diplomacy with Russia but would not firmly commit to upholding article five, which enshrines the "collective defence" principle.