The independent review is looking into foster carers’ concerns that children were wrongly removed from them by Norfolk’s social services department.
Norfolk County Council was only looking at cases since 2012, but foster carers who looked after children before then have come forward, saying they would like to contribute.
Now the investigation will review all incidents since 2010.
Ian Parker, a former chief executive of Middlesbrough council, who is leading the investigation, said: “We want to ensure that this review gives as many people as possible the opportunity to come forward and share their views, so that we can have a full picture of what the fostering service looked like and make any appropriate recommendations.
“There was always the flexibility to explore more cases and the review team has decided that it is in the best interests of both foster carers and the council to extend the scope so that the service can begin to move forward with confidence.”
Norfolk County Council started the multi-agency review in March to look at historical complaints relating to alleged unfair treatment of foster carers.
The update comes just days after Peter Barron, a team manager in Norfolk County Council’s children service’s department, was dismissed for gross misconduct.
His dismissal was understood to have related to a recommendation Mr Barron made to remove a four-year-old boy from a foster carer in 2010 in which he made statements which appeared not to be backed up by evidence.
So far 23 foster carers have come forward and the deadline for cases to be brought to the review’s attention is May 29.
As a result of issues raised by foster carers, the council is also carrying out a separate internal review to standardise practice between in-house carers and those working for foster agencies.
Members of the council’s children’s services committee will also hear an update on an internal review into fostering when they meet on May 12.