The controversial state visit of King Abdullah of Saudi Arabia, which got under way today with a lavish ceremony, has prompted new criticism over his regime's alleged role in distributing hate literature in British mosques.
The Policy Exchange thinktank found extremist literature in a quarter of the 100 mosques and Islamic institutions it visited, including London Central Mosque in Regent's Park, which is funded by Saudi Arabia.
Some of the literature advocated violent jihad, murdering gay people and stoning adulterers, its researchers found.
Most of the material is produced by agencies closely linked to the Saudi regime, according to the investigation.
The prime minister, Gordon Brown, was urged to challenge King Abdullah about the literature when he meets him tomorrow.
The government is already under pressure to raise concerns that the regime is involved in torture and other human rights abuses.
Researchers from the right-of-centre thinktank spent more than a year visiting nearly 100 Muslim religious institutions across the country, and found extremist material was available - either openly or "under the table" - in around 25.
The team collected 80 books and pamphlets, and translated the 42 that were not in English.
Extreme statements in the documents included a call for jihad against "tyrants and oppressors", which was "best done through force if possible".
Some of the publications called on British Muslims to segregrate themselves from non-Muslims, and condoned the beheading of lapsed Muslims.
Women should be subjugated and are warned not to pluck their eyebrows or wear perfume.
The study concluded: "Saudi Arabia is the ideological source of much of this sectarianism - and must be held to account for it."
The Policy Exchange director Anthony Browne said it was "clearly intolerable" that hate literature was being "peddled" at British mosques.
"The fact that the Saudi regime is producing extremist propaganda and targeting it at British Muslims must also be challenged by our own government," he said.
"It is reassuring that the majority of mosques investigated do not propagate hate literature, but much work needs to be done to ensure that a large number of leading Islamic institutions remove this sectarianism from their midst."