The pilot project is due to run until October
A human rights charity has accused Scotland's largest police force of not acting lawfully in arming some of its beat officers with Taser stun guns.
Amnesty International has written to the Scottish Justice Secretary Kenny MacAskill asking for the Strathclyde Police scheme to be halted immediately.
It claims the trial required, but did not receive, his written approval.
A Scottish government spokesman said the issue was an operational matter for Strathclyde Police.
Up to 30 officers are taking part in the six-month pilot which is due to end in October.
They have been given three days of training in the use of Tasers, which fire a 50,000-volt electrical charge and are designed to incapacitate rather than cause serious injury.
It is the first time the Tasers have been issued to beat officers in Scotland, although Strathclyde Police introduced the guns in 2005 for use by specialist firearms officers.
The £45,559 project covers areas of Glasgow and South Lanarkshire which have seen higher numbers of assaults on police officers.
Strathclyde Police Authority gave the go-ahead for the pilot scheme in February, prompting a Holyrood debate led by the Liberal Democrats.
The party argued that the issuing of the weapons to beat officers required the approval of Scottish ministers.
But Justice Secretary Kenny MacAskill said it was an operational matter for Strathclyde Police.
Amnesty International claims that assertion is wrong and Mr MacAskill is legally obliged to approve the scheme.
The charity has given the justice secretary analysis carried out by Scottish QC, Aidan O'Neill, which states that Scottish ministers are required to give written authorisation before any new schemes to arm police officers can take place.
It also claims that the Scottish government's obligations under the Scotland Act and Human Rights Act to implement a legal and administrative framework governing the use of Tasers and other firearms have not been met.
John Watson, Scottish programme director for Amnesty International, said: "We now have proof that this pilot has been pushed through without due process and the Scottish government should halt it immediately.
"The provision of firearms to ordinary officers on the beat represents a major shift in policing policy in Scotland.
"Strathclyde Police are taking a major step along the slippery slope towards an armed police force - without engaging Scottish ministers who have the responsibility to set policy on policing matters, or local politicians who are supposed to hold the police force to account."
Mr Watson said Amnesty International was not "necessarily opposed to Tasers playing a role in modern policing" but believed that the "appropriate place for firearms is in the hands of appropriately trained firearms officers rather than with ordinary officers on the beat".
Amnesty International's call for the Taser trial to be scrapped has been backed by Tam Baillie, Scotland's commissioner for children and young people.
"Arming beat officers with Tasers brings them into our communities, making them part of everyday life, and risks them being used in situations when lesser force would suffice," he said.
"Police and Scottish ministers cannot wait until there is a Taser tragedy involving a child to take action on this."
The pilot covers areas of Glasgow and South Lanarkshire
The Scottish government said the issue of firearms control was reserved to Westminster.
A spokesman said: "These devices are deployed in accordance with policy and operational guidance contained in the Association of Chief Police Officers' manual of guidance on police use of firearms.
"Firearms legislation is reserved and is the responsibility of the UK government.
"The deployment of Tasers is an operational matter for chief constables and their use must be justifiable and necessary."
Ch Sup Bob Hamilton, head of territorial policing for Strathclyde Police, said Tasers had been issued to the two sub-divisions - the city centre and Rutherglen - which had the highest level of assaults on officers.
He said: "In 2009 we lost 1,505 days through sickness of officers caused by assaults. Apart from the human cost, in financial terms this represents £260,000 worth of resources."
Ch Sup Hamilton said since the pilot programme began last month, Tasers had been deployed on four occasions, but had only been used once.
He said the regulations governing the use of Tasers, and officers' training, were exactly the same as those for firearms.
He also said the force had invited Amnesty International to examine the documentation and view training sessions, and claimed Strathclyde Police had been honest and transparent throughout the process.
Meanwhile, the Scottish Police Federation has accused Amnesty International of "scaremongering" over its claims of illegal use of Tasers.
Chairman, Les Gray, said: "We believe Taser will make a significant contribution to protecting the public. It will also help reduce the number of assaults on police officers.
"Amnesty have been guilty of scaremongering in my view and it's interesting that they have not taken up the invitation to come and see the training.
"If they did, they would see the safeguards that are in place and have the relevant law explained to them."