A leaked Prison Service memo suggests immigration officials are not deporting foreign criminals unless they are sentenced to more than a year in jail.

That could mean thousands of foreign drug dealers, thieves and fraudsters can stay in the country when they are released.

The memo, circulated to prison governors by HM Prison Service, said that "as a rule" the Border and Immigration Agency (BIA) will not try to eject foreigners sentenced to under 12 months unless the courts have recommended them for deportation.

The revelation comes after Prime Minister Gordon Brown pledged to crack down on non-UK nationals who commit crime here.

Shadow Justice Secretary Nick Herbert said at least 4,000 offenders could be benefiting from the policy every year.

"The result will be that foreign thieves, fraudsters, burglars and drugs dealers will be released back into the community," he said.

"Gordon Brown claimed that he wanted to send a message that foreign criminals would be deported.

"It takes a special kind of cynicism to promise tough action on foreign criminals while simultaneously instructing that the majority of them are to be released."

But BIA chief executive Lin Homer insisted that the Government was determined to kick out serious offenders.

"The Prime Minister was categorical earlier this year that we are committed to the removal of foreign national prisoners who commit serious crimes in this country," she said.

"Nothing in this document changes that and in fact this year we have removed more foreign nationals than ever before.

"We have repeatedly said we will target the most dangerous first which is why we are initially targeting those who have served more than 12 months."

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