The Henry Jackson Society, a neo-conservative British think tank, said a clear and "growing" link between overseas funding of hate preachers and jihadist groups accused of endorsing and promoting violence in the U.K. and Europe.
The report also urged the British government to launch a public inquiry into the alleged role of Saudi Arabia and its Gulf allies.
"While entities from across the Gulf and Iran have been guilty of advancing extremism," said report author Tom Wilson. "Those in Saudi Arabia are undoubtedly at the top of the list.
"Research indicates that some Saudi individuals and foundations have been apparently heavily involved in exporting an illiberal, bigoted Wahhabi ideology."
The Saudi Arabian embassy in London vehemently denied the report, saying the claims are "categorically false."
“We do not and will not condone the actions or ideology of violent extremism and we will not rest until these deviants and their organizations are destroyed,” read the statement from the Saudi U.K. embassy.
This isn't the first time, though, Saudi Arabia has been accused of exporting terrorism.
It has long been speculated that the Gulf kingdom is responsible for funding al-Qaida, Boko Haram and al-Shabab because they follow Wahhabism — an extremist form of Islamic ideology widely practiced in Saudi Arabia.
However, the speculation has not prevented Saudi Arabia and the West from dealing with each other in not just oil but also weapons.
Case in point: Ever since Saudi Arabia launched its invasion of Yemen in March 2015, the U.K. government has reportedly "approved no less than 194 export licenses for arms and related equipment to Saudi Arabia, worth more than £3.3billion (over $4 billion)."
This explains why British Prime Minister Theresa May, despite having the report in her personal possession for six months, has still not addressed it.
The document, according to BBC security correspondent Frank Gardner, was "largely finished and sitting on Theresa May's desk," but the government is reluctant to publish it due to its "embarrassing" content.