A Maghull Labour Councillor has met with the town's Neighbourhood Inspector to raise concerns about youngsters climbing on the roof of the old library.
Park Ward Labour Councillor Steve Kermode said young people were risking their lives climbing on the roof of the former library on Liverpool Road North.
The old library has been empty since Maghull's library was relocated to the Meadows Leisure Centre.
But the old site now attracts young people, some of whom climb on the roof.
Cllr Kermode said they were risking their lives clambering on the building.
Cllr Kermode said: "The Maghull Labour Action Team and I have received a number of concerned calls from people who have spotted young people on the roof.
"On a couple of occasions I have spoken personally to youngsters who have been climbing up there.
"They simply do not know how dangerous it is.
"Sefton Council has informed me that people can't go into the building because the roof is unsound. So these kids are risking life and limb running around on the roof."
Cllr Kermode has contacted Maghull's Neighbourhood Inspector to tackle the issue and has written to local schools to warn their pupils of the dangers.
Cllr Kermode said: "I have contacted Insp Kevin Booth to look into this issue and I have written to our local schools to ask them to warn their pupils of the dangers.
"I hope the schools can give the warning out before they break up for the summer holidays.
"I also hope that parents will warn their children.
"The roof is insecure and these young people need to be stopped from climbing up there before they are hurt."