An East Midlands police force has stopped arresting people for immigration offences because it cannot afford the expense.
The workers often have forged documents
The move comes despite the arrest and deportation last year of hundreds of foreigners who were found working in fields and food factories.
But now the immigration raids have been abandoned because the force's overtime budget has been slashed.
Deputy Chief Constable Alan Goldsmith of Lincolnshire Police said: "It is a position I would rather not be in - but it is not a core police activity.
"It supports the immigration service in their work but in terms of our work, it isn't top of the list.
"We have to put our energy on volume crime like car theft, burglaries and assaults."
We don't want these rogue 'gangmasters' using illegal workers
Almost 30 Eastern Europeans were found working illegally picking daffodils in Lincolnshire in April 2002.
Almost 900 illegal workers have been arrested in Lincolnshire in the past year, some of them with forged immigration documents.
The workers come from a variety of countries outside the European Union, including Latvia, Lithuania and Brazil.
Roger Welberrry, who grows vegetables on his farm near Boston, says he is being undercut by growers who employ workers who are not paid minimum wage.
"We don't want these rogue 'gangmasters' using illegal workers because they are disadvantaged by that.
"We look after our men," he said.
Leicestershire MP David Taylor said: "The police ought to be devoting some time to rooting out this problem."
A Home Office official told BBC News that the current situation is not acceptable and a review is being done.