Cumbria Police plans to reduce the number of officers by more than 70 because of a forecast budget shortfall.
Chief Constable Craig Mackey said civilian staff numbers would also have to be cut by 100 to trim costs.
The force is facing a cash shortfall of almost £3m by 2013, according to a report to be put before Cumbria Police Authority on Tuesday.
Mr Mackey said the number of officers would fall to 1,200 from 1,274 from March next year.
Mr Mackey said: "Our financial forecast has been produced in the most unusual and extreme economic climate.
"At this moment in time we do not know how deep the financial reductions will turn out to be.
"We have had to include some tough proposed decisions, but we continue to hold the view that Cumbria Constabulary can and will be a sustainable organisation in the longer term.
"As a result of these changes our police officer numbers will reduce from 1,274 to 1,200 by March 2011.
"Presently, for police staff, the establishment figure is 870 with 55 vacancies. With natural turnover, it is estimated that the number of staff occupying these posts will fall to 770 by the end of the financial year, and thus it may be necessary to make approximately 30 posts redundant.
"There will have to be significant changes to our structure, but these changes will further strengthen our ability to ensure the county has a top performing policing service."
Cumbria Police Authority chairman Ray Cole added: "We will work constructively with the chief constable over the coming months to continue to provide the best possible services within the constraints of the new budget."