Theresa May has defended the tough new tactics used by the Metropolitan police to stop thieves on mopeds, saying the officers are “absolutely right”.

The police released footage last month showing officers “tipping” thieves on to the ground by driving their patrol cars into the mopeds.

Diane Abbott, the shadow home secretary, tweeted: “Knocking people off bikes is potentially very dangerous. It shouldn’t be legal for anyone. Police are not above the law.” The Police Federation also said that although it broadly supported the Met’s tough tactics, the measures “breach current legislation”.

The prime minister, speaking to reporters at the G20 summit in Argentina, said the problem of moped gangs was growing and the police had her backing. “These people on these mopeds, they are acting unlawfully. They are committing crimes,” she said. “I think it’s right that we see a robust police response.”

Among those who tweeted back after Abbott’s criticism was a verified account for Camden police in north London. “Someone who’s responsible for law-making (or at least debating and ratifying new legislation) should probably realise that using tactical contact to terminate dangerous pursuits is entirely within our lawful power. And our responsibility.”

Cressida Dick, the Met police commissioner, said in an interview on Channel 5: “They’ve been risk-assessing it. These are people who have been repeatedly left in no doubt whatsoever that there’s a police car right behind them. If you look over your shoulder and drive on as fast as possible, putting the public in danger, you should expect we will come after you, and we have had a very small number of injuries.”

The Met said there had been a 36% reduction in thefts that involved mopeds or scooters since the tactics were adopted last year.