Boris Johnson has re-asserted his plans to tackle unruly and criminal behaviour by young people on buses, after Transport for London rejected claims such problems on buses are getting worse.

The Conservative candidate for Mayor of London emphasised the need for proper punishments for young people who misbehave on the city's buses.

He said: "Kids make it a living hell for people on the buses. Very often people feel more threatened than they need to, adults feel scared of kids.

"We should keep free bus travel, but if they break the behaviour code, take away their passes.

"And there are no sanctions at the moment, there is nothing to deter someone who has committed a crime from doing it again."

Mr Johnson has proposed community service for young people who commit anti-social behaviour on buses, and has pledged to permanently revoke their free bus passes.

Last month, a Harrow Times investigation revealed bus drivers in the borough come under regular attack from passengers, and often have to stop and wait for the police to arrive when young people are causing trouble.

The behaviour of children on buses has come under scrutiny after a police sergeant criticised Hatch End High School pupils for their behaviour when leaving school on public transport. Also two weeks ago, the number 18 bus route, which runs through Wembley, was named as one of the most problematic in London.

Transport for London said police figures show youth crime on buses is decreasing. The operator also said it already takes away bus passes from children who are caught misbehaving.

But Mr Johnson said only a few hundred passes are permanently revoked, and he pledged to be tougher on people who abuse public transport. He said he would introduce a ban on drinking alcohol on tube trains.

He said: "I want to see a quantum leap and instill a sense of behaviour and responsibility."