Up to 70 convicted terrorists due to be released this year will not be properly monitored, a probation chief warned yesterday.
The "high risk" extremists, some of them bomb makers, could be walking the streets after being freed on licence.
But Harry Fletcher, assistant general secretary of the National Association of Probation Officers, said cuts to services meant adequate checks could not be kept on them.
He added: "They have to be supervised by us and the police at a fairly intensive level.
"My fear is as cuts go deeper we're going to be unable to give them the close attention that we have hitherto. These men require maximum supervision and we're not going to be able to do it."
Among those set for release are Saajit Badat, jailed for 13 years in 2005 for plotting with shoe bomber Richard Reid. Also due to walk free is Moinul Abedin, jailed for 20 years in 2002 for making bomb detonators.
MPs said Government plans to water down control orders that allow dangerous individuals to be put under virtual house arrest will make the problem even worse.
Labour home affairs spokesman Gerry Sutcliffe said: "I think there is a danger that the security services are going to be overstretched.
"I would urge ministers to keep control orders in place until there is a better alternative."
Tory MP Patrick Mercer said: "The system needs a radical overhaul to protect the public."