The prospect of armed officers opening fire on arsonists during riots only risks inflaming violence, campaigners said today.
An official review of police tactics found officers could shoot arsonists as a last resort if they endanger life by attacking businesses attached to people's homes.
Sir Denis O'Connor, the chief inspector of constabulary, called for a public debate on how much force officers should use to quell disorder similar to that which swept through English cities in August.
Plastic bullets and water cannon may also be considered in the future, he said.
Sir Denis said: "Police have to be able to defend civil order but they need support from the public and others when they do that.
Half of people surveyed for the review thought police did not use enough force during the riots, while a third thought firearms should have been used against the rioters.
A quarter of the 2,000 members of the public surveyed between September 16 and 18 thought police were already using water cannon.
Sir Denis added: "If we don't raise some of these awkward issues, then we're not giving people the chance to prepare for a future where we're slightly more assured as to what will happen.
"Some new rules of engagement are necessary so the police can protect the public in confidence.
"People were burned out of their houses. We can all remember the woman leaping from the burning building in Croydon."
Polish mother Monika Konczyk, 32, was pictured leaping to safety from her flat in a blazing building in Croydon in an image which came to symbolise this summer's riots.
There has been a "long period of peace" where civil order was not top of the agenda, but now it needs to be given priority again, Sir Denis said.
"The balance of risk has changed. We have to have the means with some certainty to protect the public.
"We need some options when someone is trying to set fire to a building that someone is in, which in an urban area is beyond reckless."
The best option was to get officers on the streets as soon as possible, but the question was what should be done to protect the public while waiting for high numbers of officers to get to the scene, he said.
But Shami Chakrabarti, director of human rights campaign group Liberty, said: "How on earth would bullets have quelled and not inflamed this summer's riots? Didn't the widespread disorder all begin in Tottenham with a fatal police shooting?"
Jenny Jones, a member of the Metropolitan Police Authority, added: "Endorsing the use of live ammunition is an approval of the tactics of war on London's streets and implementing such recommendations would be madness."
Policing Minister Nick Herbert said the report was simply stating the existing law in relation to the use of lethal force by the police.
Legal advice contained in the review by Her Majesty's Inspectorate of Constabulary (HMIC) said the use of firearms could be justified when lives were being endangered by arsonists attacking commercial premises given the "immediacy of the risk and the gravity of the consequences".
Officers would still have to consider which tactics have been tried before, what happened and whether any other options were available first.
Plastic bullets and water cannon may also be considered to tackle incidents such as those seen during the summer, the review said.
There are no water cannon on the UK mainland, they cost more than £1 million each and need to be deployed in twos to be effective.
A report by the Commons Home Affairs Select Committee has said their use would have been "inappropriate as well as dangerous", adding they "could have escalated and inflamed the situation further".
Overall, police need to be better prepared, trained and ready to protect the public if they are to improve their response to similar scenes of violence and looting in the future, today's review found.
Some officers were "uncertain about the level of force and tactics than can be used lawfully during disorder".
"Some suggest this uncertainty increased after criticism following the 2009 G20 protests," the review said.
"Officers recognise that a single act of what could later be regarded as 'punitive force' can quickly change the public mood."
Commanders were also prevented from using some of the more forceful tactics during the riots due to a lack of training and resources.
Some forces ran out of shields, not all forces train to use plastic bullets in public order situations, and protective equipment was not always available.
The review also said that while it would be difficult to justify deploying soldiers on the streets, they could be used "to take over logistical roles to free police officers for public order duties".
Sir Hugh Orde, president of the Association of Chief Police Officers, said commanders making "critical decisions within volatile and fast-moving situations" to keep the public safe needed to be supported.
"When disorder occurs, the available tactics must include the necessary hard edge to resolve situations quickly and effectively," he said.
But he warned that more equipment and highly-trained officers only come at a cost.