Kyle Clifford pleaded guilty to three counts of murder, one charge of false imprisonment and two counts of possession of offensive weapons.
The criminal investigation into the alleged abduction of Alex Batty, who returned to the UK after six years abroad, has been discontinued because he and his family would not support a prosecution.
The former Labour deputy leader gave a statement to the media following the settlement being announced on Wednesday.
A seventh successive Champions League victory left Liverpool needing a point at most from their final game to guarantee top spot in the table.