Labour would overturn Chris Grayling's ban on prisoners being sent books, Sadiq Khan will confirm tomorrow.
The shadow justice secretary is expected to use a speech on criminal justice policy to confirm the opposition would scrap the controversial ban, which forms part of the government's incentives and earned privileges scheme.
A Labour government would review the scheme outright and guarantee the prisoner book ban is overturned, Khan is expected to say.
"Putting obstacles in the way of prisoners being able to read books is ludicrous," he will say.
"Educational levels in prisons are a national disgrace — 40% of those behind bars have the reading age of an 11-year-old."
Labour's commitment came after the most famous authors in Britain joined together this morning to demand Grayling reverse his prison book ban.
Figures like Salman Rushdie and Ian McEwan signed a letter to the justice secretary.
They were joined by dozens of household names, including Alan Bennett, Carol Ann Duffy, Julian Barnes, David Hare, Mark Haddon, Philip Pullman, Irvine Welsh, Nick Hornby, Ian Rankin, Joanne Harris and Jeffrey Archer.
"We are extremely concerned at new rules that ban family and friends sending in books to prisoners," the letter said.
"Whilst we understand that prisons must be able to apply incentives to reward good behaviour by prisoners, we do not believe that education and reading should be part of that policy.
"Books represent a lifeline behind bars, a way of nourishing the mind and filling the many hours that prisoners spend locked in their cells.
"In an environment with no internet access and only limited library facilities, books become all the more important."
The letter was sent to the Telegraph because it is Grayling's favourite newspaper.
"I hope that the distinguished list of writers and dramatists calling upon the Ministry of Justice to change its mind will persuade ministers to make a U-turn," Frances Crook, the chief executive of the Howard League for Penal reform, said.
"The Howard League is going to be seeking a meeting with Mr Grayling to see if we can resolve this problem and get prisoners reading."
A separate letter is been sent to the Evening Standard, signed by Simon Schama, Helena Kennedy, Howard Jacobson, Sandi Toksvig, Ruby Wax, William Boyd, Dawn French, Eric Idle, David Hare, Martin Amis and Joanna Trollope, in a campaign which is quickly turning into a who's who of British cultural life.
The Ministry of Justice ramped up its opposition to the campaign as it insisted that it would not be reviewing the policy.
"The idea that we are banning access to books for prisoners is just nonsense," Grayling said.
"We work extremely hard to keep drugs, extremist literature and other banned material out of prisons.
"Suggesting that we should suddenly start allowing people to send unlimited numbers of parcels into prisons, that might contain books or otherwise, is the surest way of seeing the amount of contraband getting in go through the roof."
Photographs of how drugs are sneaked into jails using legal products like Weetabix were sent to the press, to highlight the difficulties in dealing with contraband getting into jails.
The government faces intense criticism from right-wing figures as well as those on the left, however.
The government is going to have to give way on excluding both books and cards from the small packets ban. Recommend sooner rather than later— Louise Mensch (@LouiseMensch) March 26, 2014
Enjoyed this frm senior Tory minister on prisoner book ban: "Grayling wins the prize for the Govt's least enlightened minister." Tough field— Lucy Rigby (@LucyRigby) March 25, 2014
Tory unease over ban on books being sent to prisoners: Grayling stance 'has no backing from any quarter' http://t.co/I4cLJP0985— James Chapman (Mail) (@jameschappers) March 25, 2014
So far Downing Street is standing firm behind Grayling's decision, insisting that David Cameron backed the justice secretary completely over the issue.
"There is a statutory requirement for library services to be required in prisons, and prisoners can have up to 12 books in their cells at any one time," the prime minister's spokesman said.
"They have the opportunity to purchase books through the library. The prime minister agrees with the secretary of state for justice."
Michael Spurr, chief executive of the National Offender Management Service, insisted that prisoners had not complained about being banned from receiving books through the post.
"The whole issue that we have stopped books is a ridiculous take on a very sensible strategy," Spurr said.
"This is nonsense. There is no way we do not want to provide access to books for prisoners. I wish more would read them."
The Liberal Democrats also closed ranks against the protest yesterday, with hopes that they would disassociate themselves from the book ban dashed when Simon Hughes took to Twitter to defend the government line.
Allies of the justice secretary point out that inmates are able to use the prison library or buy books using their weekly allowance, making it irrelevant whether they can receive books or magazine subscriptions in the post.
Critics say that the money paid to prisoners is far too small for them to be able to afford books and that library services are severely lacking, leaving prisoners with a limited and generic selection.
Nicholas Jordan, an inmate at HMP Oakwood in Staffordshire, wrote to Inside Time magazine: "Some prisoners are saying they can only have 12 books in possession - lucky sods! Here at HMP Oakwood we do not have that luxury.
"There is no system in place here to purchase books from an approved supplier. We can buy games consoles or DVD players but cannot get books for love nor money. And neither can we have them sent in."
He added: "The prison library is poorly stocked and trying to order an unstocked title can lead to a three-month wait, though you usually get a slip back saying the title is 'unavailable'.
"I find all this ridiculous, especially if you want to use your time to educate yourself. So much for a 'forward thinking prison'."