Sites across Wolverhampton are currently open for a total of 656 hours per week but that will be cut back to 421 hours as the city council tries claw back £1.7 million from the service.
Bosses say the move avoids officials having to close any libraries – but campaigners who have been fighting the plans branded it a 'closure in all but name'.
From March 31, Bilston, Warstones and Wednesfield libraries will be staffed for 35 hours per week instead of 51.
Finchfield and Tettenhall libraries will open for 30 hours per week rather than 38 and 51. Ashmore Park, Pendeford and Penn libraries will open for 24 hours per week.
Ashmore Park and Penn are currently open for 38 hours while Pendeford has 51 hours. East Park, Low Hill and Spring Vale libraries will be staffed for 15 hours per week. East Park will drop from 31, Low Hill from 43 and Spring Vale from 31. Under original proposals Long Knowle library would have become self service only but it will now also be staffed for 15 hours.
At Whitmore Reans Library opening hours are being cut from 51 hours to 15. However, the main Central Library in Snow Hill, which accounts for around half of all library visits in Wolverhampton, will remain open 56 hours per week.
Pru Coleman, from the Citywide Libraries Action Group, said: "What we have said right from the start is it is closure by stealth. It's closure in all but name.
"The council is sending a message that they are quite happy for older people to be living in even more isolation then they already are and they are quite happy to take books out of the hands of children."
Councillor Elias Mattu, cabinet member for leisure and communities, said: "In an ideal world, we wouldn't need to do this – but due to Central Government cutbacks we are having to deal with an unprecedented financial challenge and must save a further £123m over the next five years, on top of the £100m the council has saved over the last few years.
"By reducing library opening hours, we have been able to make vital savings while also keeping libraries open at the times when most people want to use them – and I hope that customers agree it is better to have libraries with reduced opening hours than to not have one at all."
The council drew up the new opening times after a consultation with members of the public. Councillor Mattu added: "We have worked hard to come up with new opening times which will suit the greatest number of people, and I'd like to thank everyone who took the time and effort to complete a short survey which helped us identify the best times to open each individual branch.
"We've also listened carefully to comments about Long Knowle Library, which was originally intended to become self-service only, and have agreed that it should be staffed for part of the week."
The council also plans to introduce self-service machines into all of its libraries that do not currently have them over the coming months.
The local authority says this could enable it to keep libraries open longer than currently anticipated.
Councillor Mattu said: "We're also working with volunteers to establish friends groups and, together, these should enable us to open the libraries for longer, particularly those within community hubs. Once again, can I thank everyone who has helped shape these new opening times and reassure them that we'll be reviewing them in a few months' time to make sure they are working well for as many of our customers as possible."
When will your library be open?
Opening times for some city libraries from March 31:
Ashmore Park Library
Monday and Tuesday: 9am-1pm and 2pm-5pm. Wednesday and Sunday: Closed. Thursday: 9am-1pm. Friday: 2pm-5pm. Saturday: 10am-1pm.
Monday and Sunday: Closed. Tuesday, Thursday and Friday: 10am-5pm. Wednesday:10am-7pm. Saturday: 10am-3pm.
Blakenhall Library (self-service)
Monday to Friday: 9am-9.30am. Saturday: 9am-4pm. Sunday 10am-4pm
Monday to Thursday: 9am-7pm. Friday and Saturday: 9am-5pm. Sunday: Closed
Collingwood Library (self-service)
Monday, Thursday and Sunday: Closed. Tuesday: 10am-1pm. Wednesday and Friday: 2pm-5pm. Saturday: 10am-4pm.
East Park Library
Monday and Tuesday: 9am-1pm. Wednesday, Friday and Sunday: Closed. Thursday 2pm-5pm. Saturday 9am-1pm.
Monday: 10am-1pm and 2pm-5pm. Tuesday and Thursday: 10am-1pm and 2pm-7pm. Wednesday: 10am-1pm. Friday and Sunday: Closed. Saturday: 10am-1pm and 2pm-4pm.
Long Knowle Library
Monday, Wednesday and Saturday: 10am-1pm. Tuesday and Friday: 2pm-5pm. Thursday and Sunday: Closed.
Low Hill Library
Monday, Wednesday and Sunday: Closed. Tuesday: 2pm-5pm. Thursday: 10am-1pm and 2pm-5pm. Friday: 2pm-5pm. Saturday: 10am-1pm.
Monday, Thursday and Saturday: 10am-1pm. Tuesday: 10am-6pm. Wednesday: 1pm-5pm. Friday 2pm-5pm. Sunday: Closed
Monday, Wednesday and Sunday: Closed. Tuesday: 9am-1pm and 2pm-5pm. Thursday: 10am-1pm and 2pm-6pm. Friday: 9am-1pm. Saturday: 9am-1pm and 2pm-4pm.
Monday: Midday to 7pm. Tuesday, Wednesday and Thursday: 10am-5pm. Friday: 10am-1pm. Saturday: 10am-2pm.
Spring Vale Library
Monday, Thursday and Sunday: Closed. Tuesday and Friday: 10am-1pm. Wednesday: 2pm-6pm. Saturday: 9am-2pm
Monday: 10am-1pm and 2pm-7pm. Tuesday and Sunday: Closed. Wednesday and Thursday: 10am-1pm and 2pm-5pm. Friday and Saturday: 10am-1pm and 2pm-4pm.
Monday: 10am-7pm. Tuesday: 2pm-5pm. Wednesday: 10am-5pm. Thursday: 1pm-5pm. Friday: 10am-5pm. Saturday: 9am-2pm. Sunday: Closed.
Monday: 2pm-7pm, Tuesday, Wednesday and Thursday: 10am-5pm, Friday: 10am-1pm. Saturday: 10am-2pm. Sunday: Closed.
Whitmore Reans Library
Monday, Wednesday and Friday: 2pm-5pm. Tuesday and Saturday: 10am-1pm. Thursday and Sunday: Closed.