The government has agreed to give an extra £100m to the police to help them tackle a knife crime “epidemic” in England and Wales.

The money will mainly go to the seven forces where violence is highest. But the fund falls short of the £200m to £300m requested by police chiefs through the National Police Chiefs’ Council (NPCC) last week.

Chancellor Philip Hammond initially said police forces must use their existing budgets to tackle knife crime.

The NPCC welcomed the new money, which was announced in the chancellor’s Spring Statement, saying it would increase the number of officers patrolling crime hotspots, increase the use of stop and search and disrupt criminal gangs. The funding would also be used to fund Violence Reduction Units that seek to tackle the underlying causes of violent crime.

The chancellor’s announcement follows a spate of fatal teenage stabbings, with two 17-year-olds killed in separate knife attacks in London and Greater Manchester earlier this month.

Jodie Chesney was killed in an east London park as she played music with friends, while Yousef Ghaleb Makki was stabbed to death in the village of Hale Barns, near Altrincham.

Mr Hammond told the Commons a “wider, cross-agency response to this epidemic” was required. “Action is needed now. So the prime minister and I have decided exceptionally, to make available immediately to police forces in England an additional £100m,” he said. The money is for one year, with a longer-term funding settlement for the police expected to form part of the Spending Review.

Home Secretary Sajid Javid tweeted: “It’s vital police have the resources they need to crack down on the rising levels of knife crime. “I’ve listened and we will be giving £100m extra to forces, targeting the hardest hit areas. I’ll continue to give police the support they need.”

The forces that will mainly benefit from the new funding are: Metropolitan Police, West Midlands Police, Greater Manchester Police, Merseyside Police, South Yorkshire Police, West Yorkshire Police and South Wales Police. While 80% of the money is new Treasury funding, 20% is from the Home Office “re-prioritisation” of funds.

NPCC Chief Constable Sara Thornton said: “The additional government funding announced today is very welcome. It will help police forces strengthen our immediate response to knife crime and serious violence. “Bringing violence down is a police priority. We know what works to bring down violence.”

All police forces were undertaking a week-long intensive operation to tackle knife crime including test purchasing weapons from shops, weapons sweeps and engaging speaking to young people about the dangers of knives, she said.