These include children who have been put up for adoption.
Security fears have already forced several delays to the scheme.
The latest revelation follows a report calling for the system to be scrapped. The Database State by the Joseph Rowntree Reform Trust said ContactPoint was 'almost certainly' illegal under human rights or data protection laws. It assessed 46 public-sector databases across Government departments and said 11, including ContactPoint, should be abandoned or re-designed.
Dr Eileen Munro, an expert on child protection from the London School of Economics, said ContactPoint was not 'a solution' to child protection failings. She said, 'I've looked at many child abuse inquiries and it's not about knowing someone's phone number, it's because people don't understand the information they receive is significant and a possible indicator of abuse.'
