The British and US policy towards Iraq has "spawned new terror in the region", a think tank report has said.
The war in Iraq was threatening world stability, ORG said
The countries had tried to "keep the lid on" problems by military force and had failed to address the root causes, the Oxford Research Group warned.
It said Iran, Syria and North Korea had become "emboldened", while the Taleban was on the rise in Afghanistan.
The UK government said the past decade of foreign policy had been effective and action in Iraq was "justified".
It comes as a separate report from Oxfam said the Iraq invasion had "seriously undermined" Britain's reputation.
However, the charity warns Britain must not be reluctant to send in troops to deal with future humanitarian crises.
In a report a year ago, the Oxford Research Group (ORG) highlighted four areas that it said were contributing to world instability.
Climate change, competition for increasingly scarce resources, marginalisation of the majority of the world's population as socio-economic divisions widen, and the increasing use of military force and the further spread of military technologies were all threats.
Its latest report said these issues were still the greatest threats, but added that the ongoing war on terror and the war in Iraq were increasing the risk of future terrorist attacks on the scale of 9/11.
"Treating Iraq as part of the war on terror... created a combat training zone for jihadists," it says.
Lead study author Chris Abbott said: "There is a clear and present danger - an increasingly marginalised majority living in an environmentally constrained world, where military force is more likely to be used to control the consequences of these dangerous divisions.
"Add to this the disastrous effects of climate change, and we are looking at a highly unstable global system by the middle years of the century unless urgent action is taken now."
Iran's nuclear plan
The report, Beyond Terror: The Truth About the Real Threats to Our World, said any military intervention in Iran would be "disastrous". However, it warned that Iran should not be allowed to develop civil nuclear power.
"This would involve the development of facilities that are potential terrorist targets, as well as encourage the spread of technology and materials that could be used in the development of nuclear weapons," the report said.
It also added that the British government's decision to replace its nuclear submarine system Trident could "substantially encourage" other states to develop nuclear weapons.
A Foreign Office spokesman said the past decade of foreign policy had been effective and that the military action in Iraq was "justified".
"We have rightly focused on 'hard' security issues such as Iraq, Afghanistan, Bosnia, Kosovo and Sierra Leone as well as 'softer' issues such as climate change and poverty eradication," he added.