Home Secretary Amber Rudd cited national security reasons for not publishing the review that found a significant overseas funding for some extremist organizations in the UK in a written statement to Parliament on Wednesday.
“This is because of the volume of personal information it contains and for national security reasons,” she said.
Following three recent deadly attacks in Britain, the government has been under pressure to release the findings of the report, which was commissioned by former Prime Minister David Cameron in 2015.
Meanwhile, lawmaker Caroline Lucas, co-leader of the Green Party who has been pressing the government to release the full report, said the statement from Rudd was unacceptable.
"The statement gives absolutely no clue as to which countries foreign funding for extremism originates from - leaving the government open to further allegations of refusing to expose the role of Saudi Arabian money in terrorism in the UK," she said.
Last week, a British think tank released the report, saying foreign funding for extremism came from Persian Gulf countries, chief among them Saudi Arabia.
The Henry Jackson Society said in the report that since the 1960s, Saudi Arabia has sponsored a multi-million dollar effort to export the Wahhabi ideology across the Muslim world, including to Muslim communities in the West.