Data from the Home Office shows that Northamptonshire Police carried out 8,167 arrests in the year to March, compared with 13,796 in 2007-08.
The tally for the latest 12-month period was 6% down on the previous year.
Across England and Wales, data from all but one of the 43 police forces shows that officers conducted 698,737 arrests in 2017-18, 8% fewer than in the previous year, and half the level 10 years ago.
“This continues the downward trend seen since a peak in the year ending March 2008,” a government report said.
In the wake of the findings, the National Police Chiefs’ Council warned “proactive capabilities” to prevent crime have been “significantly curtailed”.
The reduction comes at a time when police are recording rising numbers of crimes across a number of categories including violent, knife-related and sexual offences.
Data released last week showed that Northamptonshire Police registered 55,592 crimes in the 12 months to June, roughly the same level as the previous year.
Across England and Wales, 5.6 million crimes were recorded – the highest total since the year ending March 2005.
In a statistical paper published on Thursday, the Home Office pointed to improvements in recording practices and increased confidence among victims as contributing to the rise.
Growing use of a process known as “voluntary attendance” has been cited as one potential factor behind the dip in arrests.
This is where an individual goes to a police station or any other place where a constable is present without having been arrested, for the purpose of assisting with an investigation.
Last year, a watchdog report suggested the reduction could also be linked to “resourcing pressures”.
Labour MP Yvette Cooper, who chairs the Home Affairs Select Committee, said: “These are shocking figures. Arrests have almost halved over the last 10 years and fallen by 8% in the last year alone.
“Arrests are going down at exactly the same time as serious crimes are increasing at an alarming rate.”
Chief Constable Charlie Hall, the NPCC’s lead for operations, said: “Arrests, stop and search and people tested for drink or drug driving are all at the lowest level since data has been captured.
“This reinforces our concern about growing demand and our ability to meet it with the resources we have.”
In Northamptonshire, the most common type of crime people were arrested for was violence against the person, representing 40% of arrests. A further 19% were for theft offences.
The vast majority of people arrested, 85%, were male.
A Home Office spokeswoman said: “Last year, the police made nearly 700,000 arrests across England and Wales.
“However, arrest is just one of the powers police have to tackle crime.
“Arrest figures do not capture trends such as an increase in voluntary attendance at police stations and a greater use of other outcomes, such as community resolutions.”
The Home Office report also revealed a rise in stop-and-search activity, bucking the trend across England and Wales.
In the year to March, Northamptonshire Police conducted 1,339 stops and searches – a rise of 4% on the previous 12 months.
Chief Constable Charlie Hall, National Police Chiefs’ Council lead for operations, said: “Arrests, stop and search and people tested for drink or drug driving are all at the lowest level since data has been captured.
“This reinforces our concern about growing demand and our ability to meet it with the resources we have. Our proactive capabilities that prevent crime and protect the public are significantly curtailed.”