Passions ran high as changes to the layout of Hove Library were approved after extensive debate.
Noise and the number of children using the new nursery space in the basement and back yard of the Carnegie library were irrelevant, officials said.
Councillors were told that they had to make a decision based on just the proposed physical changes to the listed building.
In an impassioned speech to Brighton and Hove City Council’s planning committee, Save Hove campaigner Valerie Paynter spoke about the number of children likely to use the space.
She said: “They said the basement could take 38 and they plan to have 16 to 32 children and to encourage parents and grandparents to come along as well as play with and read to them.
“Do the maths on that. It is clear they intend to pay for use of the basement and yard but in practice use the whole building at will.”
Some councillors questioned whether they could impose conditions to restrict noise.
Senior planning solicitor Hilary Woodward said no, and had a slide ready spelling out the law, showing that there was no change of use, and limiting councillors’ options.
She said: “The library could be converted into a nursery tomorrow as it is the same usage class.
“Physical alterations are why we are here.”
During the debate Conservative councillors Lynda Hyde and Carol Theobald both described the basement area as looking like a forgotten remnant from the 1960s.
It was a comment picked up by Green councillor Phélim Mac Cafferty in a spirited speech against the changes.
He said: “We feel a little bit like sometimes Hove Library is a little forgotten, where it might look like something out of the 70s.
“Where is the money being spent in the city.”
However, he was reminded this issue was not a planning factor and decisions about the use of the library basement were out of his hands.
The council’s Historic England “heritage champion”, Labour councillor Adrian Morris expressed his sympathy with people’s opposition to the nursery.
He said that it was in keeping with Andrew Carnegie’s vision to improve the well-being of people in Great Britain and Ireland, with an endowment of £100,000 a year.
Today his foundation continues to support projects for young people.
Councillor Morris said: “This has probably been handled badly from the beginning.
“Libraries do have to be more than a library and we have to continue to promote the vision Andrew Carnegie had.”
Councillors voted eight to two in favour of granting permission, with Councillor Mac Cafferty and fellow Green Leo Littman against the scheme.
Sarah Booker-Lewis is the Local Democracy Reporter for Brighton & Hove.