Cherie: I fear for my own children's lives

Her admission came as she told MPs of her concern about the large number of teenage fatalities in the capital and the growing trend for young people to carry and use knives.

The wife of the former prime minister urged police to "harry" known knife-carrying criminals in a bid to tackle the problem - although she stopped short of backing calls by ministers for tougher court action against offenders, insisting that police should retain the right to issue cautions for those caught with blades.

Mrs Blair's comments came as she appeared before the Commons home affairs select committee to give evidence on knife crime in her capacity as chairwoman of the Street Weapons Commission, which looks at the causes of and solutions to youth violence.

She told MPs that the death of London teenager Ben Kinsella further highlighted the problem of knife violence and confessed that she shared the fears of many parents about the threat to her own children posed by knife crime.

She said: "As a parent I am concerned about knife crime and what happens when my children go on the streets. I am not alone in that."

Mrs Blair added that there was "no magic wand solution" to knife crime - which appeared to be increasing - and said the answers included better provision of role models, improved community work and a more active approach by police.

On policing, Mrs Blair told MPs that she had been impressed by work in Hackney where local officers had been targeting known offenders and places where knives had previously been used.

"I think the idea of taking the glamour out of the crime and making highly visible policing in the way we have seen in Hackney and harrying the criminals is a good approach," she said.

"We have got to get this message across that carrying a knife is no protection at all."