Video report by Rachel Townsend
People targeting the most vulnerable and using their homes for crime is on the rise across the region.
The practice, called cuckooing, is an exploitative crime where gangs take over the homes of vulnerable people and use them as a base for criminal activity, most often involving drugs.
Many believe it is a worsening problem, and it has even recently been highlighted in the hit TV drama Line of Duty.
Now, one Merseyside housing officer has told ITV Granada Reports it is on the rise - with the number of cases he has dealt with in the past year increasing.
He wants to protect his identify so potential offenders cannot recognise him.
John - not his real name - says the pandemic has made things easier for gangs to single-out and target individuals.
He said: "It's associated mainly with people who might have mental health problems, low incomes, drug addictions.
"People who might be lonely, who might have been widowed, who might have been divorced, and might actually have very large sums of money."
"The gangs can easily trap somebody who is dependent on drugs or alcohol, who is of a low income, who might be waiting for a benefits claim to be processed, who is simply just in need of friendship during a time when other family members and friends haven't been seeing them."
There are often similarities in victim's vulnerabilities, but the crime is not limited to areas of social housing.
John added: "It can happen anywhere, not just in social housing properties it could easily be owner occupied properties, we see a lot more of it in social housing simply because we're out and about there and actually can spot the signs."
He says often the victims are left with nothing at the end of the process.
WHAT IS CUCKOOING AND HOW DO YOU SPOT IT?
The process has been called cuckooing, after the habit of some species of the bird that lay their eggs in the nests of other birds.
Police and housing teams want neighbours to be able to spot the signs of potential criminal activity as those being exploited may not recognise it.
John said: "What you're likely to see in cuckooing cases is a lot more visitors to the property staying for very short periods of time, especially cars pulling up or pulling away quickly, or people on bikes coming and getting off quite quickly.
"Curtains being closed, or blinds being drawn constantly is another factor.
"Also if it's somebody who you know and they have regular visits by care workers or care agencies, and they suddenly seem to stop, that could also be a sign that they're not engaging with agencies and has been cuckooed."
It is thought the trend is being fuelled by a rise in debt and isolation exasperated by lockdown - but when police manage to close down criminal operations, gangs simply move on to new targets.
Merseyside Police runs the 'Youknowwho' campaign to help gather information of cuckooing.
In the last year they have arrested 656 individuals, closed 172 county lines and safeguarded 272 vulnerable adults and children.
Inspector Katie Wilkinson, of Merseyside Police, says the force uses different ways to put a stop to cuckooing.
She said: "We might work with social care, we might work with housing providers, we might work with landlords to identify what support measures we can put in place for people.
"Do we need to move these people, do we need to put extra measures in place? Sometimes we'll obtain closure orders, or partial closure orders, which means the only person that's allowed inside that property is the police to come in and check that there's nobody else in there.
"That's something we use quite often to protect victims of cuckooing."
Crimestoppers say that since 2018 reports of cuckooing have risen more than four fold.
But they need the reports to keep on coming if they want to bring the perpetrators of the cruel crime to justice.
Granada Reports presenter Gamal Fahnbulleh spoke to Sir Peter Fahy, a former chief constable of Greater Manchester Police, who now works with a major housing association in the North West.
He began by asking about the signs of cuckooing.