The detention of the children of failed asylum seekers will end by next May, the government is to announce.
Deputy Prime Minister Nick Clegg is due to make an announcement about the proposal on Thursday.
The move was a key part of the Liberal Democrat manifesto and formed part of the post-election coalition agreement.
Parents awaiting forced deportation would still be held in secure houses, but their children would be assigned minders so they can move around freely.
The family section of the Yarl’s Wood detention centre in Bedfordshire will be closed and the practice of children being held will end by next May, the government said.
Labour’s John McDonnell, MP for Hayes and Harlington, raised the issue on Wednesday at prime minister’s questions.
Mr McDonnell asked David Cameron: “According to the latest statistics, over the last year, on 665 occasions, children of asylum-seekers were placed in detention centres.
“It means that this Christmas it is highly likely that there will be children in our detention centres.
“Could I ask you, and this is not a party political point, on behalf of the whole House to give this commitment – that by next Christmas there will be no children in detention centres and there never will be again?”
Mr Cameron replied: “You make an important point and we made a commitment in our coalition agreement to address this issue.
“The deputy prime minister will be making a statement tomorrow (Thursday) about how we are going to end this scandal.”
The detention centres are used to hold those who might abscond before they can be deported.
BBC home affairs correspondent Tom Symonds says the government hopes a softer approach will encourage asylum seekers not to fight their deportation.
But it is understood the change may lengthen the process and have an impact on the numbers deported.
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