Foreign prisoners are being given bribes of £500 just for returning home.
Criminals including rapists and murderers can be offered the cash in return for agreeing to go back to their home countries - as part of a package of incentives worth up to £5,000.
The money is stored on cards which can be activated once the prisoner arrives.
Ministers say the scheme, which cost £3.4 million last year, saves taxpayers' money because it discourages criminals from delaying their return with costly legal battles.
But critics said the payouts were "outrageous". Shadow justice secretary Dominic Grieve said: "It is bad enough that Gordon Brown lost control of our borders and has let thousands of foreign criminals into the country.
"Now we learn that foreign prisoners are being given cash cards loaded with hundreds of pounds of taxpayers' money. The lesson is clear: under Labour, crime pays and the taxpayer foots the bill."
Under the Facilitated Returns Scheme, foreign criminals from outside the EU who agree to return home at the end of their sentence are eligible for grants worth up to £3,000. Those who go earlier, after completing their minimum term, can access up to £5,000.
Since October, the prisoners have been entitled to £500 in cash, with £454 put on the cards on top of the £46 paid to all prisoners on release. Further sums can be paid in kind to help them set up businesses or get training. A third of the 5,395 foreign national prisoners who were returned home last year took part in the scheme.
Immigration minister Phil Woolas said: "Our Facilitated Returns Scheme saves the taxpayer money because foreign criminals are removed direct from jail or immigration detention, often before their sentence ends. This means foreign lawbreakers cannot drag out the removal process for months with frivolous appeals which clog up the legal system.
"Every day that we can get these individuals out of the country early saves taxpayers over £100 a night in detention costs. Last year we removed a record 5,400 foreign national prisoners."
