One of the most high-risk foreign criminals, released without being considered for deportation, is living in Scotland, the Home Office has said.
Home Secretary Charles Clarke has been under pressure
More than 1,000 ex-prisoners have been released since 1999, of which 79 are considered to be the most dangerous.
No details have been released about the ex-prisoner now in Scotland.
But Grampian Police has been asked by the Home Office to carry out a series of intelligence operations on foreign nationals living in the area.
Earlier this week it emerged that 1,023 foreign nationals were freed at the end of their prison sentence without consideration for deportation, sparking anger and calls for the resignation of Home Secretary Charles Clarke.
The 79 serious offenders have been identified as priority targets after being convicted of crimes including murder, rape, manslaughter and child sex offences.
On Friday, Mr Clarke revealed five of the prisoners had gone on to re-offend.
The news that there is a freed prisoner now living in Scotland came in a letter from Mr Clarke to the SNP MP Pete Wishart, who had asked questions about the matter in the Commons.
Mr Wishart said: "This devastating letter confirms that Charles Clarke has failed to contact both the Scottish Prison Service and Scottish Executive to alert them to his department's failures, despite the fact that he was aware of the situation last August.
Mr Wishart said public safety had been threatened
"Scotland has been kept in the dark for months, when our police forces could have been tasked with tracking down these dangerous individuals."
The MP for Perth and Perthshire North said public safety had been "threatened" and he was worried that the home secretary may eventually reveal that there were more cases north of the border.
In his letter, Mr Clarke said that "to the best of my knowledge" only one of the 79 most serious offenders was "residing in Scotland".
Tory MSP Bill Aitken told BBC Scotland: "I can see absolutely no mitigating factors in this matter.
"Quite clearly, the Home Office should have told the authorities in Scotland.
"We do not know how many people are out in the streets here."
Anne Begg, Labour MP for Aberdeen South, said: "This whole episode is marked by a breakdown in communication.
"My understanding is that since this has blown up, the relevant departments are speaking to one another. That's how it should have been all along."
The Scottish Executive said it was aware of the prisoner living in the country.
A spokesman said: "We are in contact with the Home Office and fully aware of the circumstances. We have been briefed on what the situation is."
Earlier in the week, First Minister Jack McConnell spoke of his "disappointment and anger" at the deportation blunder.
Hundreds of the 1,023 deportation cases have yet to be analysed.