It would hold them to account for the disappearance / death of the girl. It is their fault! As said previously, if they were working class it would have all been different, but she was a cute kid, the parents were half decent looking and they were from upper middle class background so the story was spun as it was and did as intended, sold papers in bucket loads.
It was unfit parenting, who would leave 2 children of that age alone in a hotel room at night, just because you want to go out for a nice meal?
http://www.direct.gov.uk/en/Parents/Yourchildshealthandsafety/Yourchildssafetyinthehome/DG_070594
Says it there, "it is an offence to leave a child alone if it places them at risk. Parents can be prosecuted if they leave a child unsupervised"
The fact the country have made the Mcann's minor celebs who help children, when in fact they were 2 parents who neglected their children which lead to the disappearance/death.