A new row has flared up about the use of Tasers by frontline police officers after suggestions from the Scottish Government that the pilot running in ­Strathclyde is lawful because police are covered by Crown immunity, reports The Herald newspaper.

Opposition politicians and civil rights groups reacted with alarm to the claim that officers are immune from prosecution. They warned that it would be dangerous and wrong to take such an approach.

There is also concern at disparities between this statement and those made in Parliament earlier this year in which Crown immunity was not mentioned and Justice Secretary Kenny MacAskill told MSPs that decisions on Tasers were for individual police forces.

The Herald revealed last month that a 50-page legal report, by a leading QC commissioned by Amnesty International, warned that Scottish ministers should have given written authorisation before any new schemes to arm police officers can take place.

Amnesty's calls for the Taser pilot to be suspended and for ministers to set guidance have been supported by Labour and the LibDems. Alan Miller, chairman of Scotland's Human Rights Commission, and Tam Baillie, the Children's Commissioner, also backed calls for a halt to the pilot.

However, Strathclyde Police believe the pilot is lawful and they and the Scottish Police Federation have argued that Tasers will protect officers from a growing number of assaults.

Strathclyde Police Authority was given the guidance by Government officials on June 8 after concerns were raised about the legality of the pilot.

In a memo to authority members, Stephen Curran, convener of Strathclyde Police Authority, wrote: "Strathclyde Police Authority received official opinion from the Scottish Government that the police in Scotland do not require ministerial approval to possess or use Taser because of the effect of the principle of Crown immunity.

"Based on the legal argument advanced by the Scottish Government, Strathclyde Police Authority is satisfied that no written consent is required from Scottish ministers for the deployment of Taser."

John Watson, Scottish programme director for Amnesty International, said: ""If this represents the Scottish Government's justification for their position on the Taser pilot, then why did they not say so before?

"The Scottish Government position rests on the idea that police officers are not subject to any law which does not specifically name them. This is simply wrong, and would beg the question as to which other laws the police do not need to obey."

"Amnesty believes that Tasers have a role to play in modern policing but the right place for these weapons is in the hands of specialist and highly trained firearms officers rather than with ordinary officers on the beat."

Tony Kelly, a human rights solicitor, warned that claiming Crown immunity for officers is wrong and does not remove the need to be compliant with the European Convention of Human Rights (ECHR).

He said: "Police officers cannot claim Crown immunity. They hold office under the Crown; they swear allegiance to the sovereign. That does not make them servants of the Crown – a very peculiar position with very peculiar consequences. One need only pause for a moment to think of the consequences of police officers claiming immunity as Crown servants for the very notion of the rule of law.

"Would they be immune from prosecution and from civil suit? And why has it not been claimed thus far? It has been unequivocally stated in the leading textbook on constitutional law that police officers are not servants of the Crown."

Liberal Democrat justice spokesman Robert Brown said the position adds chaos to ­confusion. He said: "The Scottish Government are coming up with more and more bizarre arguments to justify their position."

James Kelly, Labour's community safety spokesman, said: "We want to see our police officers properly protected, but it is vital we ensure whatever steps taken are within the law."

Campbell Corrigan, assistant chief constable of Strathclyde Police, said: "Our position is that the chief constable has the lawful authority to carry out the Taser pilot and that it is ECHR compliant."

A spokesman for the Scottish Government said: "The Scottish Government's position remains that the deployment of tasers is an operational matter for chief constables and their use must be justifiable and necessary."