Bereaved parents and anti-knife crime campaigners have called on the government to declare an emergency on violent crime.
OperationShutdown saw supporters march in London asking the next prime minister to call a meeting of the government’s Cobra emergency committee to deal with the issue.
Some demonstrators had their hands covered in fake blood.
The Home Office said £200m would be spent on reducing youth violence.
The protest started in Trafalgar Square and ended at Parliament where some demonstrators doused the gates in fake blood as others chanted: “Whose streets? Our streets. Whose children? Our children.”
There was also a short skit depicting Conservative leadership candidates Jeremy Hunt and Boris Johnson as Brexit-obsessed, and dismissive of other issues.
Violent crime recorded by police in England and Wales rose by 19% in a year, in 2018, according to Home Office figures.
The number of homicides – including murder and manslaughter – rose from 649 to 739, an increase of 14%, in the 12 months to the end of September 2018.
It was the the highest total for such crimes since 2007.
Grace Aloba, 42, from Hackney, east London, whose 18-year-old son was murdered in 2015, said: “There’s not enough help for the victims afterwards. I’ve faced many sleepless nights, and I’m still dealing with depression on a daily basis; it’s not easy.
“Hopefully, the politicians will pull their socks up and help us. It’s an epidemic now.
“It’s not just in London, but country-wide.”
Ms Aloba’s son Isaiah Ekpaloba was an aspiring rapper who was killed after a botched robbery when the target fought back.
Jen Lock, from Ealing, west London, who started the campaign Lives Instead Of Knives 18 months, said: “I want to see politicians accept the problem and deal with it.
“There needs to be more action. We need more police – it’s a national epidemic.”
The Home Office said it was “determined to end the cycle of violent crime which is destroying so many young lives”.
It said more than £200m would be spent on “projects steering young people away from violence”.
Sajid Javid today chaired a serious violence taskforce that included Met Commissioner Cressida Dick and London Mayor Sadiq Khan, the Home Office said.