Police officers must remember they are “the servants and not the masters” of the people, the head of the police watchdog said yesterday as he condemned the practice of concealing shoulder numbers as “unacceptable”.

Nick Hardwick, the chairman of the Independent Police Complaints Commission (IPCC), said he would appear before the Home Affairs Select Committee as the fallout surrounding allegations into the use of police force at the G20 protests grew more acrimonious.

Mr Hardwick said he had “serious concerns” about front-line supervision of officers at this month’s demonstrations. The IPCC launched a third investigation yesterday into police tactics after a 23-year-old London man claimed he was assaulted by a Metropolitan Police officer. “Why was that happening? Why did the supervisor not stop them? What does that say about what your state of mind is?” he asked. “You were expecting trouble?”