Cash-strapped councils are dishing out as little as 5p per person on library books, figures obtained by the Press Association have revealed.
Library funding has seen a drop of £5.5 million on book expenditure across the biggest local authorities in the country over the last four years.
Responding to the "outrageous" findings, War Horse author Michael Morpurgo warned that depriving people of access to the written word was the "unseen cancer of society".
The former children's laureate urged the Government to "look inside themselves" or risk "letting down a generation of children".
Freedom of information requests were sent to 46 councils in some of the biggest cities and counties in the UK, of which 42 replied.
In Birmingham, the country's second largest city, spending per person had dived by 79% since 2011-12, with residents having just 19p each spent on their reading, down from 91p.
This is still more than double what residents of Newcastle receive, as the city council forked out only 9p per head on books for their libraries in 2015-16.
But both are overshadowed by the London borough of Redbridge, where spending dropped 97%, leaving each person with less than 5p for library reading material, instead of the £1.70 being spent four years earlier.
Councils blamed the tumbling figures on "substantial Government budget reductions" which had placed their finances under strain.
Morpurgo, the author of 130 titles, told the Press Association: "We're not just letting down a generation of children, we're letting down a generation of people and that's what seems to be happening now."
He pointed to the "vast, vast numbers of children and adults" who are illiterate or cannot afford books as a reason libraries should be supported.
"You are going to get an alienated people and one of the great alienations is to be unaware of your stories; where you come from, what your history is, if you don't feel part of anything," he added.
"If you don't belong to anything, why should you then be a responsible citizen? There is no investment for you in this society.
"Society is about weaving somehow, but there has to be something which holds the weaving together, this tapestry, and if you unpick the threads things will not hold, it will fall apart.
"Our literacy, our right to literature and our enjoyment of literature is one of those really important threads."
Of the 42 councils that responded - including Manchester, Leeds, Cardiff and Cornwall - only Westminster and City of London spent more than £1.62 per head on books.
The findings come after analysis by the Chartered Institute of Public Finance and Accountancy (Cipfa) revealed this month that overall spending on public libraries had dipped by £25 million in the last year.
Morpurgo said: "This is the unseen cancer of society.
"When this kind of depriving of people of what they thought they would grow up with, whether it's the National Health Service, which is completely wonderful, but when you remove doctors from it and nurses from it... that is going to upset people and make them feel hard done by.
"And it is the same with libraries and on it goes and on it goes. If our politicians say we want a society for all our people then do it."
He added: "I think (the Government) should look inside themselves and ask each of them - Theresa May - how did you first begin to think that ideas and stories were important?
"There was, for every single one of those people, a children's book which got them going into the world of reading and knowledge and understanding."
His criticism was echoed by Cathy Cassidy, the young adults' fiction writer, who said: "Libraries, for me, were a stepladder out of the small life that had been mapped out for me, a path to hopes, dreams and ambitions I hadn't dared dream of."
She added: "Unless we stand together to stop the decimation of our libraries, we will see every last local library close, and that is shameful and terrifying in the fifth richest country in the world, a country that claims to value culture, creativity and learning."
Ian Stephens, from the Local Government Association, which represents hundreds of councils in England and Wales, said authorities recognise the "tremendous role" libraries play in society.
He added: "However, local authorities have experienced substantial central government budget reductions which forced them to reduce spending."
A spokesman for the Department for Culture, Media and Sport said: "The Libraries Taskforce has published a strategy for the service in England to ensure they are more resilient and better utilised by local authorities.
"This includes a new £4 million fund for projects such as literacy schemes, improving access to technology, and increasing the number of children visiting libraries."