The Friends of Waterloo Library have launched a petition calling on Lambeth Council to save the much-valued community facility in Lower Marsh.
Waterloo was one of four Lambeth libraries named this month by council leader Steve Reed as being too expensive to run. A review of the borough's library service is due to be launched in April.
The present Waterloo Library and job shop in Lower Marsh opened 11 years ago as an interim measure to replace the previous North Lambeth Library (itself a temporary building) which closed when the building was declared unsafe in 2001. Waterloo has been without a permanent public library since 1966.
Members of the newly re-formed Friends of Waterloo Library were collecting signatures on their new petition in Lower Marsh on Friday.
"When the Friends were formed in 2004/5 they were an active group who realised that there was always a chance that friends would be needed," says local resident and author Wendy Mathews.
"Now we know from the local government cuts that we are really needed. We are under threat and this is the time to re-form the Friends."
Cllr Reed has said that any library buildings that are closed will not be sold by Lambeth Council. He has also suggested that libraries could be taken over by community groups.
The Friends of Waterloo Library say that it is too early to consider taking over the library.
"I think that's in the future," says Mrs Mathews. "We'll have to face that if it comes to it. But this is one reason for re-forming the Friends now: we can start discussing these points and working out what we could, or should, or might be able to do."
Despite the current library's modest size it hosts regular public events including a monthly book group and activities for children.
• The Friends of Waterloo Library are inviting local residents to two special events in the library on Tuesday 1 and Friday 4 March between 3pm and 6pm.
As well as a chance to sign the petition, there will be storytelling, a raffle and a poster design competition.