The terrorist groups have a total of 65,000 fighters in Syria that are poised to fill the vacuum should ISIS be defeated, according to The Sunday Times.
In the report, which has been seen by MailOnline, the author's find that some of the groups have designs on attacking the west, with the number one group named as Jabhat al-Nusra, Al-Qaeda's affiliate.
It warns that British and coalition attacks on ISIS could be a 'strategic failure' if it overlooks other groups operating in the country and that sixty per cent of rebel groups are takfiri terrorists.
Jabhat al Nusra already controls a significant amount of territory in Syria's northwestern province of Idlib.
'The current focus on the military defeat of ISIS does not consider the other groups in Syria [and around the world] with exactly the same global ideology and ambitions.
'Our study of 48 rebel factions in Syria revealed that 33 percent - nearly 100,000 fighters - follow the same ideology as ISIS.'
Ed Husain, director of strategy at the CRG told The Sunday Times that ISIS ideology has 'no border or barrier' and has already demonstrated that it can inspire its followers to 'kill just as easily in Paris as it can in Raqqa.'
'We must wake up to the fact that this is global, Unless we uproot the ideology from spreading, we will find ourselves dealing with the same problem over and over again,' he said.
The report also warns against coalition attempts to distinguish between moderate rebels and 'unacceptable extremists', because of the overlap of groups on the ground.
Given the fluid and changing nature of frontlines in Syria, groups often share resources and work together to fight Assad forces, which include Hezbollah fighters.
Jabhat al-Nusra's leader Abu Muhammad Golani denied any intention to attack the west in an interview with Al Jazeera earlier this year, however the group's spokesman Abu Firas al-Suri said the group's goals are not limited to Syria.
Jaish al-Islam, the group identified as having the most fighters at 17,000, are solely focused on fighting the Syrian government. The vast majority of their fighters are Syrian, and not foreign terrorists.
The report also lists Ahrar al-Sham, a salafi group strongest in northern Syria which has ideology similar to ISIS, Dailymail reported.
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