Birds of a Feather actress Linda Robson also joined the march, with her son Louis who was with Ben after the attack.
Mrs Robson called for "stronger deterrents" to knife crime saying: "If you can do that to another human being, you are not going to be able to take that out by sending them to prison for five or six years."
Cherie Blair, appearing as Ms Booth before the Commons Home Affairs Select Committee, said: "As a parent I am concerned about what's happening when my children are on the street and I know I am not unique in that by any means.
"I think the evidence that we heard from people on the street and indeed the figures we were getting from hospitals, is that there are more people presenting with injuries caused in this way.
"Because this is almost a new phenomenon - that younger children are carrying knives and, sadly, using them - the statistics are not looking at the right areas."
According to the British Crime Survey (BCS), overall violent crime has decreased by 41% since a peak in 1995. Knives are used in about 8% of violent incidents, according to the BCS, a level that has largely remained the same during the past decade.
But the BCS figures do not include under-16s, something which the Home Secretary Jacqui Smith announced this month would change.
Richard Garside, the director of the Centre of Crime and Justice Studies at Kings College London, said: "If you look at the figures for the last 10 years the number of knife victims has remained relatively stable - although there have been spikes - at 200 to 220 a year.
"But there is some evidence the demographic has changed. The average age of homicide victims overall has been going down, with younger and younger victims."
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