The survey out today records 15 crimes against birds of prey in North Yorkshire last year – including the shooting of five buzzards, the destruction of a marsh harrier nest and the poisoning of a red kite.
The second worst was Bedfordshire with five confirmed incidents. Joint third were Herefordshire and Cumbria with four apiece.
Nationally the charity recorded 68 incidents, but said these were likely to be the tip of the iceberg, with many more going undetected or unreported.
But the charity says enforcement is also a major issue – there were just four raptor persecution-related prosecutions in the UK in 2017 and only a single conviction.
Bob Elliot, RSPB Head of Investigations, said: “North Yorkshire has plenty to be proud of but its notorious reputation for raptor persecution must be addressed.
“The persecution of birds of prey is a widespread problem in the UK, and is affecting some of our most loved and vulnerable species, like owls and eagles.
“Every week the RSPB’s Investigations team get reports of yet another raptor being shot, trapped or poisoned.
“But for every report we receive, scientific studies suggest there are many more that go undetected and unreported.
“As such, these figures only scratch the surface of the true extent of raptor persecution in the UK.”
The RSPB is calling for a licensing system for driven grouse shooting to tackler wider issues of intensive management including the draining and burning on fragile peat bogs.
It says a “fair set of rules” could help ensure shoots operated “legally and sustainably” including an option to restrict or remove a licence where staff were found guilty of the most serious crimes against wildlife.
Between 2012 and 2017 there were 71 confirmed bird of prey crime incidents in North Yorkshire, nearly three times as many as Powys in Wales, which is the second worst county, with 25 recorded over the same period.
Last year there were also two poisoned buzzards and one shot sparrowhawk in East Yorkshire, while a buzzard was shot in South Yorkshire.
In 2016 there were 81 confirmed incidents across the UK and 19 in Yorkshire.
Amanda Anderson, Director of the Moorland Association, which represents many grouse moor owners, said: “It is encouraging to see that the number of persecution incidents, both across the UK and in North Yorkshire specifically, continue to decline significantly.
"This is what we all want to see.
"Of course, more can be done and the best way to achieve progress is for people, including RSPB, to continue to work together constructively.
“The Moorland Association is committed to the eradication of all forms of wildlife crime.
“Any incident of bird of prey persecution is unacceptable and the full force of the law should be felt by those breaking it."