Three specialist units are being built in high-security jails to separate extremist inmates from the rest of the prison population.
The Government is creating the "jails within jails" in a bid to tackle radicalisation, and to stop convicts with dangerous Islamist or far-right ideologies from influencing their peers.
In total, the centres will be able to accommodate up to 28 extremists - and the first unit at HMP Frankland in Durham is expected to be operational within weeks.
Once a prisoner is moved to one of the units, which will be completely separate from the main wing of the jail, their case will be reviewed by experts every three months to see whether the threat they pose to vulnerable inmates has sufficiently reduced.
It is believed that a decision is yet to be made on which inmates should become the first to be moved to the specialist units.
Prisons minister Sam Gyimah said: "Any form of extremism must be defeated wherever it is found, and it is right that we separate those who pose the greatest risk in order to limit their influence over other prisoners."
Earlier this month, a new taskforce of 100 counter-terrorism experts was launched as part of government plans to tackle "poisonous" extremism behind bars.
The specialist team is designed to advise jails across England and Wales on how to deal with specific threats, and train prison workers on effective ways to deter offenders from being lured into extremism.
Figures suggest that more than 1,000 prisoners are identified as extremist or vulnerable to extremism at any one time.
Last year, a Government-ordered review concluded that Islamist extremism is a growing problem within jails.
That assessment uncovered evidence of offenders expressing support for Islamic State, and "charismatic" prisoners acting as "self-styled emirs" to radicalise fellow inmates.
When the taskforce was unveiled, the chief executive of a foundation which works to tackle extremism told Sky News that radicalisation had reached "unprecedented levels" in the nation's jails.
Hanif Qadir, a former Taliban fighter, said: "It's since the inception of Islamic State and the calling to jihad by IS. Over the last three to four years, the growth of violent extremism within prisons has been on an unimaginable scale.
"At the moment, the problem in our prisons is very, very concerning and we need to deal with it rapidly."