The NHS expert put forward to advise Ashya King's parents in Spain is a consultant clinical oncologist with experience in treating children with cancer, the Department of Health says.
A spokesperson told ITV News the consultant has not treated Ashya before and has no previous relationship with Southampton General Hospital, where the five-year-old was treated in the UK.
The Department added that it had chosen the oncologist but would not be releasing their name.
The head of the police force which applied for a European Arrest warrant against the parents of Ashya King has now urged their release.
A British mother whose son's life was saved by proton therapy has told ITV that she defied NHS doctors' advice to pursue the treatment.
The parents of Ashya King said they took him out of a hospital to seek proton beam treatment which is not available under the NHS.