Civil servants working on a new strategy to combat knife and gun crime in England and Wales said offenders may have been “encouraged” by a lack of resources, the document seen by the BBC and the Guardian says.
The leak comes after the government had insisted the fall in officer numbers has not contributed to the spike in crimes.
More than 50 people have already died on the streets of London this year as a result of a series of stabbings and shootings.
Home secretary Amber Rudd will later launch a new Serious Violence Strategy in an attempt to turn the tide on violent crime – including £40m in funding and a drive to crack down on the drugs industry.
But a draft of the strategy from February said an increase in recorded sex offences since 2012 coupled with a fall in officer numbers has put forces under serious strain.
"So resources dedicated to serious violence have come under pressure and charge rates have dropped. This may have encouraged offenders,” it said.
It noted that resource pressure is not the “main driver” but has "likely contributed", and points to the fact that forces will the biggest falls in personnel are not seeing the biggest rises in violent crime.
Rudd will today lay out plans to crack down on the sale and possession of knives and acid and measures to prevent the trafficking of drugs from cities into less urban areas.
Ahead of the launch, she said it was a "mistake" and "disservice" to communities and families to blame police numbers.
She told BBC Radio 4's Today programme serious violence was a "complex crime" and "not all about police numbers", adding that she had not seen the leaked report.
Later today, she will say: “This strategy represents a real step-change in the way we think about and respond to these personal tragedies, these gruesome violent crimes which dominate the front pages of our newspapers with seemingly depressing regularity.
“We will take the comprehensive approach necessary to make sure that our sons and daughters are protected and our streets are safe.”
And she will add: “I am clear that we must do whatever it takes to tackle this so that no parent has to bury their child.”
The strategy will include a new £11m Early Intervention Youth Fund for community projects to help young people live lives free from violence.
It identifies the changing drugs market – in particular the devastating impact of crack cocaine – as a key driver of the violence harming communities.