Police fear becoming the focus of public anger at government cuts and that repeated clashes with demonstrators risk damaging their reputation, a top officer has told the Guardian.

Sir Hugh Orde, president of the Association of Chief Police Officers, said it was crucial that police do not appear to be "an arm of the state" who are being used to allow the government to "impose cuts".

His comments came as the Metropolitan police force faced questions over its handling of violent student protests.

Police expect a string of future demonstrations as government spending cuts begin to bite. While they have started with students, public sector workers are facing mass sackings.

Past protests have damaged the police's reputation with sections of the community, notably the 1980s miners' strike.

Asked if there was a danger to the police's reputation by repeated clashes at demonstrations, Orde told the Guardian: "Yes, if it is allowed to be played as the cops acting as an arm of the state, delivering the elected government's will, rather than protecting the rights of the citizen.

"We need to be clear we are doing it as operationally independent, and not subject to influence by anyone as to how we do it.

"As long as that is maintained we can rebut any allegations that we are doing what we are told by our political masters to advance a political agenda. The police are not against anybody."

Orde, who was praised when he was in charge of policing divided communities in Northern Ireland, said of the expected protests: "The predictable consequence is that the police become the focus of people's anger. Any time citizens in uniform comes up against the citizen, relationships suffer."

A former top Scotland Yard officer said police must develop new tactics if they are to stop protesters rampaging through London's streets.

The Metropolitan police deployed an array of tactics to try to stop violence, but failed when small groups of demonstrators managed to outmanoeuvre them. The chief tactic used was kettling, where sections of the crowd are penned into an area, or contained, as police try to maintain order.

But the former Met deputy assistant commissioner Brian Paddick said: "The protesters seem to have learned, by doing this on a weekly basis, how to outmanoeuvre the containment tactics. They splinter into smaller groups, running at speed en masse, rather than staying in one group.

"There needs to be a radical rethink. I can not see how conventional police tactics can contain this level of violent demonstration."

Scotland Yard faced a series of questions over the riot that marred the protests, which also saw a student left with serious head injuries after being struck by a truncheon.

Police were under pressure on three fronts following the violence. The first was the attack on the royal car, which was one of the most serious breaches of royal security in years.

The second was the loss of control of the streets of the capital, with attacks on the Treasury, supreme court, a Christmas tree in Trafalgar Square and other properties in central London.

The third front on which police were being challenged was the alleged mistreatment of protesters, ranging from allegations of brutality to the "kettling". Police said 33 people had been arrested during the protests. A Met spokesperson said: "The majority of these people have been bailed pending further inquiries. Some remain in custody at central London police stations. None have been charged at present."

Tonight Scotland Yard announced a major criminal investigation into student demonstrations over the last month.