Referring foreign national offenders in Leicestershire to the Home Office for deportation cost the criminal justice system around £7.7 million last year.
Foreign national offenders are classed as any offender who is not a UK citizen. Their offences could have been committed overseas or in the UK.
For those who committed offences overseas, those crimes might not come to light until the individual is brought to the attention of police in this country, sometimes for minor offences.
Under freedom of movement rules, background checks are not currently carried out on EU nationals who come to the UK, although this could change when the Brexit deal is finalised.
People from outside the EU, and those entering the country via certain visa routes, do have to disclose their background.
During 2017, 110 offenders who passed through Leicestershire Police custody suites were referred to the Home Office.
The Office for National Statistics estimates the cost of dealing with such criminals to be about £70,000 per offender.
The figures were revealed as Detective Sergeant Gary Bee and Pc Tony Andrews from Operation Advenus gave a presentation on their work to the Leicestershire Safer Communities Strategy Board at a County Hall meeting.
Operation Advenus investigates cases for referral to the Home Office and the immigration service.
Det Sgt Bee said: “The misconception is that there is an application process, but that is not the case.
“The reality is that people [from the EU] with convictions, and often very serious convictions, can move to the UK with an entirely clean slate.
“It is startling, but this is the situation we face.
“The worrying thing is that often the first time we come into contact with these people is often when we get them in custody.”
At the meeting the officers outlined their operation and asked local councillors and council officers to raise any concerns they have about people within their areas at the earliest possible opportunity.
The police want to encourage community partners to report any suspicions about individuals to them in an attempt to make communities safer.
Det Sgt Bee said: “We’re asking our partners in the community to alert us as soon as they can. We want to see improved information sharing to help us tackle this problem.
“When someone comes into custody there is a process that we follow to identify foreign national offenders, but before that point they could have been someone’s noisy neighbour or a person responsible for anti-social behaviour in a community.”
An average of 120 foreign national offenders pass through Leicestershire Police’s custody suites per month. The 110 offenders referred to the Home Office in 2017 were able to be referred for deportation because of the severity of their criminal backgrounds.
Offenders can be referred to the Home Office if background checks carried out by the police show that they have committed a sex offence which resulted in a more than one day imprisonment, served a sentence of 12 months to four years within the past 10 years and any offence that resulted in a more than four year sentence.
If approved for deportation, a referral usually results in the offender being banned from the UK for 10 years or more.
Pc Andrews said: “These costs mentioned are just to manage offenders who are referred to the Home Office.
“If we were talking about [dealing with] a murder or a stranger rape, then the costs are unquantifiable.”
He added: “These people serve their time overseas and then come here with a clean slate.
“[But] murderers, rapists and drug dealers don’t stop being those things just because they move to a new country.
“Until we come into contact with them, often for a nominal offence, we have no idea of their background.”
Det Sgt Bee, of the Leicestershire Police Force Intelligence Bureau, said that Operation Advenus is working to protect the people of the county and not to single out innocent foreigners.
He said : “It’s important to say we’re not targeting foreign nationals here, we’re targeting foreign national offenders.”