- Treasury has blocked just £61,000 in 59 accounts of suspected terrorists
- David Anderson QC, independent reviewer of terrorism legislation, said figures were 'remarkably low'
- Comes as identity of 15-year-old schoolgirl who joined ISIS is revealed
- Sharmeena Begum led three best friends to join terror group last month
Despite more than 600 British jihadists having fled for Syria and Iraq, only 25 terror suspects are currently subject to asset-freezing orders.
In total, just £61,000 in 59 bank accounts belonging to suspected terrorists has been blocked by the Treasury, a report has found.
The report, by the independent reviewer of terror legislation David Anderson QC, showed another 28 people have had their bank accounts in the country frozen under European orders.
It showed there were eight new Treasury designations in the year to September 2014 under the Terrorist Asset-Freezing Act 2010 - a sharp decline from 162 in 2008.
Mr Anderson concluded the figures for assets frozen were 'remarkably low.
He said they indicate asset-freezing has played only a 'marginal role' in combating 'the most serious terrorist threat of the present time'.
Sharmeena Begum was revealed as the 15-year-old British schoolgirl who led three others to join ISIS
'Travel to and from such conflict zones, together with the preparation of terrorist acts, often requires funding and facilitation,' he said.
'There has been an attempt to use asset-freezing legislation to respond to the threat posed by UK residents who travel to and from Syria and Iraq for the purposes of terrorism.
'But bearing in mind that over 600 Britons have travelled out there, the small number of designations indicates that asset-freezing has played only a marginal role in combating the most serious terrorist threat of the present time.'
The report will raise serious concerns as increasingly numbers of young homegrown jihadists continue to abandon their homes in favour of Islamic State.
It comes as the identity of a 15-year-old London schoolgirl who led her three best friends to Syria after becoming radicalised was revealed.
Sharmeena Begum fled Britain to join Islamic State in December - and was the first of four GCSE pupils at the same school to become jihadi brides.
She is believed to be in the IS stronghold of Raqqa with Bethnal Green Academy pupils Kadiza Sultana, 16, Shamima Begum, 15, and Amira Abase, 15, who travelled to Syria last month.
Yesterday, video emerged apparently showing the three runaway British schoolgirls in Turkey before they fled into Syria to become brides for Islamic State militants.
The footage is believed to have been taken by a foreign spy who was arrested for helping the trio cross the border.
The girls are said to have first arrived at Istanbul Ataturk Airport before heading to the southern city of Gaziantep close to the Syrian border.