More needs to be done to tackle the use of excessive force and abuse of power among the Metropolitan Police's unit of specially-trained riot officers, the police watchdog has said.
A review into complaints against the Met's Territorial Support Group (TSG) was launched in the wake of high-profile cases such as the allegations made against Pc Simon Harwood following the death of newspaper vendor Ian Tomlinson during the G20 protests.
While the number of complaints has fallen from "unacceptably high" levels in 2009, the Independent Police Complaints Commission (IPCC) said, there are still a high proportion arising from unplanned stop and searches and instances of unlawful arrests.
There are 793 TSG officers working in London, tasked with dealing with public disorder outbursts, protecting against terrorism and cutting high-concern crime such as knife attacks.
A prevailing culture of aggressive and violent behaviour, particularly towards young black men, has featured heavily in allegations made against TSG officers, the IPCC said.
The IPCC, which looked at complaints and conduct cases involving TSG officers between 2008 and 2012, said allegations against TSG officers frequently fall in the "oppressive conduct" category.
The specially-trained officers, who work in demanding policing environments and high-crime areas, have more complaints made against them than their borough support unit (BSU) colleagues carrying out a similar role.
Four independent investigations arose from policing of the G20 protest in April 2009, the Commission said.
In the first case, Pc Harwood, a TSG officer, was charged and acquitted following a four-week trial for the manslaughter of Mr Tomlinson. He was subsequently dismissed without notice, following a misconduct hearing.
Pc Harwood hit Mr Tomlinson with a baton and shoved him to the ground on the fringes of the protests.
In other examples, a 29-year-old TSG officer was prosecuted for assault after pushing a 16-year-old through a shop window in the High Street in Bromley, south east London, in February 2010 when he approached to stop and search him. The officer resigned and was sentenced to 150 hours' unpaid work.
However, the number of complaints fell "substantially" in the final 36 months of the period, with the number of complaints against TSG officers at the 2009 G20 demonstrations higher than those at the student and Trades Union Congress protests in 2010/2011.
Within complaints made against TSG officers, 28 were referred to the IPCC for investigation, of which six were referred back to the Met Police and one was withdrawn.
Within the 28 complaints referred to the IPCC, 20 arose from unplanned street encounters, four were from planned operations and four from public order incidents.
Of the 28 complaints, 12 included allegations of racial discrimination.
Meanwhile, 23 of the 28 cases reviewed were stop and search encounters, of which only four cases resulted in items being seized.
The IPCC found a high proportion of complaints arising from unplanned stop and search encounters.
The Commission said it was concerned at the small number of upheld complaints, including in circumstances where the officers' actions were "questionable".
The TSG needs to look more closely at its complaints handling to see if it is properly upholding complaints where a member of the public has a legitimate grievance, the IPCC recommended.
The Met Police said they will "strive" to decrease the number of complaints even further by increasing the understanding of the work of the TSG.
Deputy Assistant Commissioner Maxine De Brunner said: "The TSG have made many improvements in recent years, which is evident in the decrease in the number of complaints, the sustained decline shows that the programme of work is having an impact.
"I am very proud that officers who have to face some of the most difficult situations are doing so in a highly professional way."