The 36-year-old failed to turn up for work at the University of York's Goodricke College and at the height of the search 100 officers were involved in the investigation.

From next month there will be seven officers involved in the investigation which has so far cost around £770,000.

Assistant Chief Constable Tim Madgwick said that North Yorkshire Police had conducted a thorough and detailed investigation which had included the use of specialist resources for a considerable period of time.

He said: "During the past sixteen months, as leads are followed, investigated and actions completed, we are now in a position where there is no longer a requirement for the level of resources allocated to the inquiry.

The decision to reduce dedicated resources has been taken after several months of further review and detailed scrutiny.

"The investigation remains open and we will be continuously reviewed with the necessary resources allocated should any new evidence or lines of enquiry emerge."

A documentary about Miss Lawrence's disappearance will be broadcast next month on Channel 4 and a dedicated response team and phone number will be allocated to respond to any calls received as a result.

Martin Dales, Peter Lawrence's friend and spokesman, said: "It is both regrettable but quite understandable that after 16 months searching for Claudia, North Yorkshire police have to be realistic about the number of officers that can be devoted to her disappearance.

It is clear that other police forces might well have given up on a case such as hers and it is good to hear that there is no let up in their determination to find out what has happened to Claudia."