At a time when young people in London and their families are worrying about knife crime and gang culture, Mayor Boris Johnson seems to be spending his time plotting to remove the Police Commissioner.

Concern among London Labour MPs that we were getting neither reliable information nor action from the Mayor led us to approach Home Secretary Jacqui Smith. She met with us last week to begin a direct dialogue with her and senior police officers.

We discussed methods of prevention, detection and punishment to deal with the current problem of knife crime. None of the issues are simple – from parenting to stop-and-search to sentencing. The problem is not made easier by media grandstanding and simplistic rhetoric from politicians.

Figures just released by the police show knife offences are down 14 per cent in the past year and violence against young people is also down. But I also believe there is under-reporting of knife incidents that stop short of physical harm. Carrying, producing and threatening with a knife are real problems, if my conversations with constituents of all ages are to be believed.

I think the Government is right to introduce the presumption of prosecution for all knife offences and a real risk of custody. I know from many years of representing and prosecuting young offenders as a criminal lawyer that the risk of prison and sometimes the actuality has a salutary effect.

Additional police resources and concentration on catching those who are carrying will have an effect. If you think you will be caught and see your friends being caught and sent down, you are likely to stop taking a knife out with you, we were told by Deputy Assistant Commissioner Alf Hitchcock, national lead officer on knife crime.

We discussed prevention and providing constructive things for young people to do. Earlier this year Ken Livingstone announced a £79m investment in young Londoners, £59m of which would come from the Government. Ealing’s share was £1.5m. To greater fanfare, Boris Johnson said he would spend £700,000 on three projects, which is a start but less than one per cent of Ken’s commitment.