Two black men were stopped and searched by London police after they bumped fists because officers suspected they were dealing drugs, a watchdog report has revealed.
The Independent Office for Police Conduct (IOPC) was investigating five searches of black men by Metropolitan Police officers.
The watchdog said taken together, these incidents showed poor communication and police were too ready to use force rather than seeking cooperation.
On two occasions, the smell of cannabis was the only reason for a stop and search.
Officers did not understand why their actions were seen as discriminatory, it added.
IOPC director Sal Naseem said stop and search had been “undermined” in London by these problems.
But the Met said stop and search is a “vital and legitimate power” – police chief Cressida Dick has repeatedly backed the tactic in the capital
It comes with black Londoners trust in the Met at a low following Black Lives Matter protests over summer.
Demonstrators condemned racial bias in British policing, after the death of African American man George Floyd at the hands of US police.
Mr Naseem said the IOPC findings “mirror concerns expressed to us by communities across London” and there is “clearly much room for improvement”.
The watchdog criticised Met officers for failing to switch on body worn cameras from the start of stop and search incidents.
Mayor of London Sadiq Khan has repeatedly described body worn video as a “game changer” that provides evidence of an encounter to improve public confidence.
The report also said officers were slow to end searches of black Londoners despite not finding any evidence of criminality on a number of occasions.
Mr Naseem said the force should “reflect on the impact this kind of decision making is having”.
“There is also a need to better support officers on the frontline to do their jobs effectively with the right training and supervision so they aren’t subjected to further complaints and investigation,” he said.
The IOPC has made 11 recommendations to the Met following the investigation, and the force has accepted all of them.
They include tackling unconscious bias, scrapping stop and search based on the smell of cannabis alone, and reducing the use of handcuffs during searches.
A Met spokesperson said:”We recognise that how the tactic is approached, trained and delivered, remains a significant area of concern for communities across the capital and we are committed to ensuring that every encounter is conducted professionally with respect and courtesy.
“We understand the impact that even a thoroughly professional encounter can have on an individual stopped and searched, and that its impact can resonate more widely with communities.”