Up to ten British women and their children are said to have left the group’s so-called caliphate in Syria and could join around 350 extremists already back on UK soil.
There has been much debate about what to do with returning jihadis. Many fear they pose a very serious terror threat due to the training they may have received from hardened extremists.
Of the 350 who have come back, figures released last year showed only 54 individuals had been prosecuted and 30 more faced charges.
A Mail on Sunday investigation discovered a number of returned jihadis roaming free on the streets of Britain.
Although many were sent away by husbands preparing for a ‘final stand’ against its enemies, some had become disillusioned with the terror group’s oppressive regime, the sources claimed.
The 28-year-old went on: ‘Dozens of the women have left Isil areas and tried to get to Turkey since the beginning of the year, including about five-10 Britons.
‘When your husband is dead, or the situation is dangerous, the women are brought to houses where they live all together.
She claimed the men have become ‘even more brutal’ as ISIS loses territory to both the Syrian regime and the Iraqi army.
Most escapees are believed to pay smugglers thousands of pounds to get across the border to Turkey where they seek help from embassies.
Many of those returning were trained in the use of explosives and firearms as they took part in ISIS’s bloody rampage, The Times has reported.
The paper states that intelligence gathered on them is often covert or sensitive meaning it cannot be used in court.
The flood of new jihadists is stretching the UK’s security security services to breaking point, with up to 30 officers required to provide 24-hour monitoring of just one suspect.
It comes after a British defector from the group told how up to 300 British members of ISIS remain in the Syrian warzone.
Experts believe they may be in communication with those who have returned, raising the fear of further plots.