Surrey Police knew murdered school girl Milly Dowler’s phone had been hacked by the News of the World back in 2002.

The force has admitted for the first time it was aware the Walton teenager’s voicemails had been accessed by the paper back in 2002.

Chief Constable Mark Rowley said in a letter to the Commons Home Affairs Select Committee that a call from the paper in April that year made it apparent that someone working for, or on behalf of, the paper had hacked into the phone.

He said the force’s priority at the time was Operation Ruby, to find the missing schoolgirl, who was 13 when she disappeared walking home from Walton station.

No criminal investigation was launched at the time and an inquiry is currently ongoing as to why that was the case.

Chief Con Rowley said: “The inquiry team’s current analysis suggests that the Operation Ruby team focussed on retrieving any evidence the NOTW had that could assist in the investigation into Milly Dowler’s disappearance.

“At that time, the focus and priority of the investigation was to find Milly who had then been missing for over three weeks and significant resources were deployed to achieve this objective.”

The inquiry team is also looking at why Surrey Police failed to pass on its evidence that NOTW had illegally accessed Milly’s voicemails, when the Metropolitan Police conducted its original phone hacking investigation in 2006.

Keith Vaz, chairman of the committee reviewing the hacking allegations, said: “Had Surrey Police acted in 2002, it may have prevented the culture of hacking becoming endemic at News of the World. This was a serious omission.”

Chief Con Rowley said police watchdog - the Independent Police Complaints Commission (IPCC) - is currently investigation an allegation that a Detective Constable shared information about the Milly Dowler murder case with journalists.

The force also took action against an officer in April 2002 after he passed confidential details about the investigation to a retired police office.

There was no evidence to suggest he provided journalists with information, but he was instantly and permanently removed from Operation Ruby.

Former bouncer Levi Bellfield was convicted this year of the abduction and murder of Milly Dowler.