NO-ONE is suggesting staff at the Russian Consulate in Edinburgh had any knowledge of the nerve agent attack on ex-spy Sergei Skripal and his daughter.

But the SNP is right to say that the ever-widening investigation into the incident in Salisbury which left 21 people requiring medical treatment should not be curtailed by diplomatic immunity.

The Kremlin has denied any involvement in the attack but if police wish to speak to Russian officials in Edinburgh or London, steps should be taken to speak to anyone of interest. As Stephen Gethins MP said detectives should have access to all Russian officials.

The UK government can request a waiver of diplomatic immunity so that police can interview people of interest and if officers feel that is the correct course of action, nothing should not stand in the way of the investigation.

After all, there has been a chemical attack on British soil which has endangered the lives of British citizens, including a police officer who was first on the scene.

The brazen use of nerve agent must not go unpunished, otherwise hostile foreign powers will believe it is open season. As many have said, using a chemical weapon on British soil is tantamount to an act of war.

It is time for decisive action against those who have no respect for the rule of international law. Every stone must looked under, every person of interest spoken to so that foreign governments understand they can not use this country as a base for criminal action.