At the same time, Saudi Arabia has led an international campaign to primarily blame its neighbor Qatar for the surge in extremist violence in recent years. Saudi Arabia, the United Arab Emirates and several Arab allies have cut off travel, trade and diplomatic relations with Qatar as punishment, and they set a deadline of Wednesday night for Qatar to comply with a sweeping list of demands aimed at curtailing its influence and independence, including shutting down its pioneering Arab news network, Al Jazeera.

“It is complete, utter hypocrisy,” said Tom Wilson, the author of the Henry Jackson Society report.

The report set off new debate here only in part because of its implications for the feud in the Persian Gulf, which threatens to divide the Western-backed alliance against the militants of the Islamic State, also known as ISIS or ISIL. Britain is also reeling from a string of deadly terrorist attacks by Islamist extremists in recent weeks, including a suicide bombing in May at an Ariana Grande concert in Manchester and an attack last month on and around London Bridge.

The attention to Saudi Arabia also comes at a time when Ms. May’s political opponents are ratcheting up their denunciations of her Conservative government’s support for the two-year Saudi-led war in Yemen, which has plunged that impoverished country into a humanitarian catastrophe of disease and famine with no end in sight. (Saudi Arabia says the campaign there is essential to keep power away from the Houthis, a Yemeni faction aligned with Iran.)

The study of Saudi extremism was initiated more than a year ago by Ms. May’s predecessor, Prime Minister David Cameron, also a Conservative. He agreed to it partly to win the support of another party, the Liberal Democrats, for airstrikes against the Islamic State in Syria, and on Wednesday the Liberal Democrats accused Ms. May of putting Saudi business deals ahead of public safety by declining to disclose the study’s findings.

“We hear regularly about the Saudi arms deals or ministers going to Riyadh to kowtow before their royal family, but yet our government won’t release a report that will clearly criticize Saudi Arabia,” Timothy Farron, the leader of the Liberal Democrats, said in a statement.