Deputy Prime Minister Nick Clegg said "the full force of the law" should not be thrown at the parents of Ashya King and called for the family to be reunited.
He told Good Morning Britain: "My heart does go out to them [Ashya's parents] and I'm like any parent.
"It seems to me...that Mr and Mrs King are in a state of great anguish and have taken this exceptional step of removing their child from hospital and going elsewhere because that's what they think is right for their child.
"We can debate whether we think that's right or not but that's clearly their motive and I don't think that kind of motive is the reason why we should be throwing the full force of the law at them.
"I do want to see the family reunited and I think it's awful Ashya is in a hospital on his own."
Ashya King's parents told the Daily Mail they fled the UK after being told NHS treatments would leave him with life-long disabilities.
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.