The document titled The Round Up says hundreds of people have been detained and then deported as a result of the joint visits, which have taken place as often as every two weeks in the capital’s central boroughs.
Freedom of information responses found 133 rough sleepers were detained in eight London boroughs last year.
And a two-month pilot programme in Westminster saw 127 rough sleepers deported to both EU and non-EU countries.
The joint visits appear to have been used to gather data to feed into a database called Chain (Combined Homelessness and Information Network) owned by the Mayor of London’s office.
Chain data includes details such as nationality and location, and revealed that as of March 2016, around 59% of the 8,096 people seen sleeping rough in London were non-UK nationals.
The database is available to the Home Office, which said Chain data helped locate migrant rough sleepers.
The report found in some cases people being referred directly by charities to Home Office immigration teams.
In addition, rather than being entirely “voluntary”, such removals came under the threat of force, Corporate Watch said.
The findings have been met with concern by migrants’ rights groups.
The charities claim the complex situations of those living rough on London’s streets required them to work with partners including the Home Office. They said their outreach teams prioritise moving people from the streets.
The Home Office declined to say how many were detained or deported using Chain data.
The Mayor of London’s office said Chain data helped identify which homeless people are entitled to help in the UK. It said some of those who were not entitled to help had their routes home funded.
In May 2016, new rules made it easier for the government to arrest and deport European rough sleepers.
The Home Office policy means that sleeping rough is considered an “abuse” of freedom of movement, the Independent reported.
Corporate Watch also alleged that St Mungo’s and Thames Reach were contracted by the Greater London Authority (GLA) on a “payment by numbers” scheme.
This meant fees depended on the number of homeless people who left the UK.
..for destitute non-UK rough sleepers, their best option is to come off the streets and be helped to return home voluntarilyThames Reach
In a statement sent to The Huffington Post UK, Thames Reach said: “In order to work effectively we have developed a wide range of partnerships that enable us to help rough sleepers move away from the streets.
“These include partnerships with councils and housing organisations, health services, faith groups, employers and training providers, the police and, in the last few years, with migrant charities and the Home Office.
“Thames Reach also knows from years of experience that for destitute non-UK rough sleepers, their best option is to come off the streets and be helped to return home voluntarily.”
The starting point for our work is the belief that sleeping on the streets is dangerous and harmful to people’s health, regardless of where you are from.St Mungo's
St Mungo’s said in a statement: “Our Outreach teams go out day and night to work with anyone who is sleeping rough and offer the right support to help people off the streets and to rebuild their lives.
“At St Mungo’s we recognise that these solutions involve housing, but also, crucially, services for physical and mental health, substance misuse treatment, skills and work.
“The starting point for our work is the belief that sleeping on the streets is dangerous and harmful to people’s health, regardless of where you are from.
“People can have complex situations and we would always work with each person with dignity and respect to help them move away from the street for good.”
A spokesperson for the Mayor of London’s office told the Guardian: “We fund routes home, which is £599,406 a year, and contract manage St Mungo’s to provide the service.
“Some of these rough sleepers who include asylum seekers and refugees may be eligible for support in the UK while others are not and are returned to their home countries.”
We explore all options in terms of employment and housing, and have helped hundreds of rough sleepers in the past 12 months.Change, Grow, Live
In a statement sent to HuffPost UK, Change, Grow, Live (CGL) said: “Change, grow, live (CGL) do all we can to help rough sleepers to get help, regardless of their background or nationality.
“We explore all options in terms of employment and housing, and have helped hundreds of rough sleepers in the past 12 months.
“We work with a number of local authorities and statutory agencies around the country to reduce the risks faced by rough sleepers and find solutions to their sometimes complex needs.
Change, Grow, Live (CGL) said that should employment or housing not be found for an EU national, it would “offer supported reconnection to that home country or somewhere they have relatives, and liaise with services there to ensure they have a place to go.”
“When there is no other option and the person has refused reconnection, they are unable to work and cannot be housed, there is little alternative to them going back to their home country,” it added.
[Chain] provides data relating to the location of rough sleepers including migrant rough sleepers.Home Office
A Home Office spokesperson told the Guardian: “The GLA holds a large database of homeless people in the capital – The Combined Homelessness and Information Network (Chain). Its analysis is made available to the Home Office by the GLA.
“It provides data relating to the location of rough sleepers including migrant rough sleepers.
“We do not publish figures for the number of individuals found during rough-sleeping operations, and are unable to discuss ongoing operational activity for security reasons.”
And in a statement sent later to HuffPost UK, it added: “It is unacceptable for anyone to come to the UK with the intention of sleeping rough and/or to beg on the streets to support themselves.
“Those who are encountered rough sleeping may be misusing their free movement rights. We will take action, including removal from the UK where appropriate, against EEA nationals who refuse to find alternative accommodation.
“We work closely with local councils and homelessness outreach services to ensure that those who are vulnerable receive the care they need.”
HuffPost UK has contacted the mayor of London’s office for further comment.