Professor Alan Miller, chairman of the Scottish Human Rights Commission, said that the introduction of a standing firearms authority for 275 officers across the country was not simply an operational matter for the Chief Constable alone to decide.
His response contradicts the view of Sir Stephen House himself, the Scottish Police Authority (SPA), which has oversight of the single force, and the Scottish Government.
It comes amid continuing public concern at armed officers appearing at unexpected locations, from a baker's shop to a charity run.
Professor Miller said that Scottish Ministers have principal responsibility for policing policy and for ensuring that "police power, priorities and style are exercised in a way that protects the human rights of everyone in Scotland".
In a statement, he said: "Guns are lethal weapons. They have the power to kill and to cause serious harm. Their use by police officers must always be monitored and regulated carefully. Any potential increase in their use is of particular concern when it comes to our human rights."
He said the commission recognised that specially trained armed police performed a necessary and important function when protecting people's lives in violent situations.
He reiterated the commission's view that lethal force should only be used where there is a real and immediate risk to life.
"Introducing guns to standard policing duties, even where officers are fully trained, increases the presence of lethal weapons on Scotland's streets," he said. "This kind of change should only take place with extreme caution and with appropriate scrutiny by all of the public bodies that have responsibility for policing policy and operations. We do not believe this issue is simply an operational matter for Police Scotland."
A spokeswoman for the SPA said: "As the national oversight body for policing in Scotland, the SPA has made clear that there is a need for ongoing information, transparency and reassurance on this issue. That is why the matter was the subject of detailed consideration at our last public meeting at the end of June.
"In our consideration of the issue, SPA members stressed that public concerns, particularly in the north of Scotland, were real and an ongoing process of information and engagement was required to address them."
She said the SPA would keep the issue under review, "particularly around the areas of risk, health and safety, and complaints".
Meanwhile, Police Scotland's Chief Superintendent Elaine Ferguson, said: "The Chief Constable's duty of operational independence requires him to make decisions on policing free of political interference, however, as an organisation we continue to engage with elected representatives, Scottish Parliament, the Scottish Police Authority and the wider public."
She said the current deployment of a limited numbers of armed officers was subject to continual review. Deputy Chief Constable for Crime and Operational Support Iain Livingstone confirmed last week that a meeting in the autumn would discuss a motion from Highland Council that the force should reconsider the matter in light of public concern.
A Scottish Government spokesman insisted armed policing, which was long standing in the country, was an operational matter which was for the Chief Constable to decide. He said: "Over 98 per cent of police remain unarmed with the small number of remaining officers, only 275 out of 17,244-strong workforce, working across the whole of Scotland. These officers work on a shift basis meaning only a small number will be deployed in our communities at any one time."