Lambeth's cabinet has agreed to carry out an options appraisal on the future of Waterloo Library in Lower Marsh with the intention of providing a permanent building for the service.
"We've set a very modest aspiration of intending to move the Waterloo Library – which has been in a Portakabin for the best part of 30 to 40 years – into an actual proper building," said Cllr Sally Prentice, the borough's cabinet member for culture, at Monday night's cabinet meeting in Lambeth Town Hall.
"It really isn't acceptable in the 21st century to be running a public service out of a Portakabin."
Tim O'Dell of Lambeth Unison struck a note of caution, warning the cabinet that small libraries like Waterloo could be reduced to "a shelf of books with maybe a storyteller visiting".
However, Cllr Prentice insisted that the library service would remain in the hands of paid staff.
"One of the key themes of the consultation was that residents of Lambeth wanted a professionally led library service," she said.
"The library which I used a child, which is run by Oxfordshire County Council, is now run exclusively by volunteers.
"Here in Lambeth that is not a direction of travel that we want to go to.
"The challenge that faces us ... is to use the new budgets and the space in the libraries to bring in other organisations that are complementary to the library's core purpose to generate income that will help us to maintain the buildings, to have the facilities open for longer hours and using modern technology."