John Dickinson said he was disappointed by the news and concerned that the case should continue to be pursued vigorously. He was told the news of Judge Renaud Van Ruymbeke's decision personally.

Caroline, from Launceston, Cornwall, was 13 when she was killed in a youth hostel while on a school trip to Pleine Fougeres, Brittany, on 18 July 1996.

John Dickinson: Shocked and disappointed at the decision

Mr Dickinson said: "It's not a case of him quitting, so I'm told. It's a matter of his expertise being needed and requested in Paris.

"He has evidently not wished to leave Caroline's case until he was absolutely sure everything was being done."

"The family are disappointed and concerned about the future of the case, although we appreciate his wish to move on.

"Unfortunately we can't, and our priority remains the same - all efforts must be made to catch Caroline's killer."

The hostel where Caroline was killed

A replacement for Judge Van Ruymbeke has yet to be appointed. He has led the murder investigation since 1997.

Mr Dickinson said he was not sure how the investigation would continue, but said: "It's the larger net that's now being pulled in".

"With DNA evidence, if the man is called in for a test he will be caught," he said.