An investigation into the foreign funding and support of jihadi groups that was authorised by David Cameron may never be published, the Home Office has admitted.
The inquiry into revenue streams for extremist groups operating in the UK was commissioned by the former prime minister and is thought to focus on Saudi Arabia, which has repeatedly been highlighted by European leaders as a funding source for Islamist jihadis.
The investigation was launched as part of a deal with the Liberal Democrats in exchange for the party supporting the extension of British airstrikes against Islamic State into Syria in December 2015.
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Tom Brake, the Lib Dem foreign affairs spokesman, has written to the prime minister asking her to confirm that the investigation will not be shelved.
The Observer reported in January last year that the Home Office’s extremism analysis unit had been directed by Downing Street to investigate overseas funding of extremist groups in the UK, with findings to be shown to Theresa May, then home secretary, and Cameron.
However, 18 months later, the Home Office confirmed the report had not yet been completed and said it would not necessarily be published, calling the contents “very sensitive”.
A decision would be taken “after the election by the next government” about the future of the investigation, a Home Office spokesman said.
In his letter to May, Brake wrote: “As home secretary at the time, your department was one of those leading on the report. Eighteen months later, and following two horrific terrorist attacks by British-born citizens, that report still remains incomplete and unpublished.
“It is no secret that Saudi Arabia in particular provides funding to hundreds of mosques in the UK, espousing a very hardline Wahhabist interpretation of Islam. It is often in these institutions that British extremism takes root.”
The contents of the report may prove politically as well as legally sensitive. Saudi Arabia, which has been a funding source for fundamentalist Islamist preachers and mosques, was visited by May earlier this year.
Last December, a leaked report from Germany’s federal intelligence service accused several Gulf groups of funding religious schools and radical Salafist preachers in mosques, calling it “a long-term strategy of influence”.
The Lib Dem leader, Tim Farron, said he felt the government had not held up its side of the bargain made ahead of the vote on airstrikes. The report must be published when it was completed, he insisted, despite the Home Office caution that information in the document would be sensitive.
“That short-sighted approach needs to change. It is critical that these extreme, hardline views are confronted head on, and that those who fund them are called out publicly,” he said.
“If the Conservatives are serious about stopping terrorism on our shores, they must stop stalling and reopen investigation into foreign funding of violent extremism in the UK.”