About 1,000 Muslim prisoners are at risk of being radicalised in British jails as part of 'terrorist academies'.
Lord Falconer has warned the number is higher than those who have travelled to fight in the Middle East and Syria.
The shadow justice secretary said that extreme Islamist inmates were taking control of some wings.
A report due on how to stop extremism in prison still hasn't been published, he added. He suggested that Michael Gove, the justice secretary, was concentrating on the EU referendum.