Police officers are "frustrated" that people they suspect are in the UK illegally are not being properly dealt with by immigration officials.
Police Federation chairman Jan Berry told the BBC officers feel they are "reinjecting" illegal immigrants back into society to commit further crimes.
Ms Berry said police feel let down by a lack of proper investigation by the Border and Immigration Agency (BIA).
The BIA said it was committed to deporting foreign criminals.
"It's like a double whammy that not only do you not expect them to go into the system"
Ms Berry said officers were frustrated at the advice given to them by the BIA about suspect individuals.
She said the agency was telling police to let people go with the instruction to make their own way to immigration centres later.
"It's terribly frustrating for police officers where they have a person who they believe is in the country unlawfully," Ms Berry said.
"It's like a double whammy that not only do you not expect them to go into the system, you're also re-injecting them back into society where they can carry on committing crime."
A BBC Radio 5 Live investigation has spoken to failed asylum seekers arrested for selling counterfeit DVDs who have been released to carrying on offending.
A BIA spokesman said it was committed to the removal of foreign national criminals and that last year more were removed than ever before.
To hear more, listen to 5 Live Report on BBC Radio 5 Live at 1930 GMT on Sunday, 13 January.
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