The police watchdog has urged the Metropolitan Police to reduce the use of excessive force following complaints against specialist riot officers.
The Independent Police Complaints Commission (IPCC) looked at complaints against the Territorial Support Group.
The IPCC said public confidence would be damaged unless the TSG improved its stop and searches procedure and how it dealt with public order situations.
The Met said it would “strive” to reduce the number of complaints.
A review was begun by the IPCC into complaints against the TSG in 2010 and the inquiry looked at complaints and conduct cases between 2008 and 2012.
There are 793 Territorial Support Group (TSG) officers in London. They deal with public order issues, terrorism and crimes such as knife attacks.
During the G20 protests in the City of London in 2009, newspaper vendor Ian Tomlinson, 47, was hit with a baton and shoved to the ground. He died minutes later.
PC Simon Harwood, a TSG officer, was acquitted of his manslaughter in July but he was sacked after being found guilty of breaching standards by a Metropolitan Police disciplinary panel.
Four independent investigations arose in relation to the G20 protests, the watchdog said.
The IPCC said there had been a “sustained decline” in complaints against TSG officers since 2009 but it said more work needed to be done.
It called for the force to address “underlying issues” relating to allegations of racist behaviour by officers, which featured heavily in the complaints.
The report found many of the allegations fell in the “oppressive conduct” category.
In total 28 complaints were referred to the IPCC for investigation, of which six were referred back to the Met and one was withdrawn.
Of the 28, 20 related to unplanned street encounters, four were the result of planned operations and four from public order incidents. A total of 23 of the 28 complaints were about stop and searches.
Twelve complaints included allegations of racial discrimination.
The IPCC said it was concerned about the small number of complaints that were upheld.
The Met said it would “continue to strive to decrease the number of complaints” and would work to “improve officers’ behaviour by education and increase the scrutiny of officers’ actions”.
It said community reference groups had been created which scrutinised stop and search, recruitment selection and complaints against TSG officers.
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.”