Seven libraries across the borough could have their hours slashed in an attempt to save money.
Letters announcing the review have been sent out last week by the county council to library workers in Cockermouth, Maryport, Seaton, Moorclose, Aspatria, Keswick and Wigton libraries.
Workington and Silloth libraries will not be affected by the proposal.
The county council will enter into formal consultation with staff on Tuesday
Proposals include lunch time and Saturday closures.
A council spokesman said: "Government cuts to the county council over the last few years have resulted in huge financial pressures, including those on libraries.
"We have made every effort to manage this without affecting the service the public receives and as a result avoided the wholesale changes to library services which have occurred elsewhere in the country."
Friends of Cockermouth Library was formed earlier this month to fight cuts and a proposed transfer of the service to the town council.
A petition launched by the group, which fears the transfer will mean the loss of true library services, has already attracted 150 signatures.
The group is due meet at Wild Zucchinis, on Station Street, at 10.30am on Monday and people are welcome to attend.
The county council is due to run a public consultation into the changes from December 5 to 22.
A council spokesman said: "A public consultation on these proposals, which include some changes to library opening hours and a potential community asset transfer of Cockermouth Library, will be held in December for a period of three weeks.
"A final decision on these proposals will be confirmed by councillors in the New Year."
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