Police have been accused of abusing stop-and-search powers, days after the home secretary, Sajid Javid, made it easier for officers to use the controversial measures.

Campaigners claim that the Metropolitan police are frequently misusing section 60 orders, which allow officers to search anyone in an area for a limited period if serious violence is anticipated.

Two weeks ago Javid made it easier for police in England and Wales to search people without reasonable suspicion under section 60 in an attempt to tackle knife crime.

However, Stopwatch, which campaigns for fair and effective policing, has said it was receiving complaints from Londoners about what it described as a routine “abuse” of the power. One recent case received by the group involved an unmarked police car mounting a pavement in Waltham Forest, east London, prompting a group of black teenagers to run. They were all then all then apprehended without officers providing reasonable grounds for suspicion.

Another involved an Asian teenager being threatened with a taser and forced to lie on the ground outside a fast-food restaurant in Brixton, south London, before being searched under section 60. When his father went to complain at the local police station, campaigners claim he was told that there was no record of the incident. Another case, also in Brixton and reported last month, involved a black family who were driving home being targeted and the driver, the father, being “aggressively” searched under section 60. In all the cases no weapons were seized, which the group says undermines its effectiveness.

Katrina Ffrench, chief executive of Stopwatch, said: “We are also concerned that the way it is being used is damaging community relations. These people are less likely to want to engage with the police; it’s toxifying relations and undermining efforts to address knife crime, because you’re alienating the very communities that may have information.”

Even before Javid’s intervention, the Met had been accused of rolling out section 60 by stealth with a 400% rise in the use of those powers in 2018 compared with the year before. Figures obtained by Channel 4 News revealed that 7,328 section 60 orders were used in 2018, a 417% rise compared with the previous year.

A Met statement said: “We strongly believe in the use of this preventative power and will continue to use this important tactic to keep Londoners safe.” Javid said stop and search was a “hugely effective power when it comes to disrupting crime, taking weapons off our streets and keeping us safe”.

According to analysis by the Guardian, the Metropolitan police had already increased its use of stop and search last year, with a 19% rise in searches carried out among London’s minority black population, which was targeted more than the white population.

Searches of black people, said the research, were less likely to detect crime than those conducted on white people, and most stops found no wrongdoing.