Lies would not have convinced every EU nation, plus Canada, Australia and all the other well informed liberal democracies in the world, and the Labour Party's leadership.

Unless you think they are all in on the lie.
I think that just Russia is lying again, as it has done so often in recent years, e.g. lied about cheating in the Olympics, lied about its intervention in Crimea, lied about the shooting down of a Malaysian airliner, lied about their murder of Litvinenko,.........