Failures in police intelligence will be investigated in the wake of violent student fees protests which exposed a response that "clearly did not go to plan", the Policing minister said.
Britain's largest force, criticised for its heavy-handed tactics during the G20 protests last year, got the balance wrong between cracking down on violence and allowing peaceful protests, Nick Herbert said.
But the blame for the "appalling scenes" lay "squarely and solely" with those who carried out the violence, he said.
More than 40 Met officers were injured and 50 people arrested as a hard core of protesters intent on violence occupied 30 Millbank in central London, smashing windows, lighting fires and throwing missiles, including a fire extinguisher, from a roof. The violence was sparked as a peaceful march involving around 50,000 students and lecturers protesting against a proposed fee hike and university funding cuts passed the landmark building on the River Thames.
Prime Minister David Cameron called for "the full force of the law" to be used against those responsible and welcomed an inquiry by the Metropolitan Police Commissioner Sir Paul Stephenson.
Mr Herbert urged MPs to await the outcome of the review "rather than speculate on the intelligence failure", saying the inquiry will include "an examination of why numbers and violence on this scale were not anticipated".
The force planned to deploy just 225 officers to the protests, but had to double the numbers sent to the scene as the situation developed.
There was "a question about how and when they deployed", but lessons will be learned, he said.
"The police have to strike a balance between dealing promptly and robustly with violent and unlawful activity on the one hand, and allowing the right to protest on the other. Clearly in this case the balance was wrong but these are difficult decisions and they are not taken lightly."
Sir Paul admitted his force underestimated the number of people who would join the march and mistakenly categorised the event as a low risk to the capital. Branding the violence an "embarrassment to London and to us", he pledged to examine what went wrong and apologised to those left inside 30 Millbank, who included senior politicians, for their "traumatic experience".