Foreign policy reporter Adam Goldman explains who Mohammed Emwazi is and how The Washington Post discovered his identity. (Gillian Brockell and Alice Li/The Washington Post)

After the unmasking of Islamic State executioner “Jihadi John” as a West London computer programmer named Mohammed Emwazi, Asim Qureshi looked into the television cameras here and made an explosive assertion: Britain, he suggested, had created its own monster.

A senior member of a rights group that had sought to advise Emwazi before his transformation into a now-infamous killer, Qureshi insisted that the pressure tactics of overzealous secret service agents bent on turning him into an informant had contributed to the metamorphosis of a person who had once been a “kind,” “gentle” and “beautiful young man.” And he was not the first case. British intelligence had used similar tactics, Qureshi charged, on one of the men who had beheaded a British soldier on a London street in broad daylight in 2013.

The nation reacted fast, condemning Qureshi and the group he serves — Cage, whose outreach director is a former Guantanamo detainee — as part of the problem. Prime Minister David Cameron called Qureshi’s comments “reprehensible.” The Daily Mail decried Cage on its front page as “Jihadi John apologists.” A government body on Saturday reaffirmed an investigation into Cage’s biggest donors. Qureshi — who levied his charges in a Cage news conference held after The Washington Post unmasked Emwazi on Thursday — said he began taking extra security precautions this weekend after receiving death threats against him and his family.

“What we are seeing is an unwillingness to be introspective about the role we play in alienating our own youth,” Qureshi said.

The reaction here suggests a powerful friction in Britain — as well as France and Denmark and other countries that have borne the marks in recent weeks of Islamist terrorism — over the tactics security agencies are deploying to curb a new generation of homegrown terrorists. The basic question: Is the intelligence community taking the right approach?

Scores of hostages, including Westerners, have been killed by the Islamic State since 2014.

Suggestions that Emwazi may have had radical leanings prior to his first known run in with British intelligence in 2009 indicate he may have been on an inexorable path to becoming Jihadi John before its alleged involvement. Yet even some here who completely distance themselves from Qureshi’s assertions are questioning whether the security agencies are spending too much time seeking to cultivate and turn prospective extremists, rather than arrest and prosecute them.

“Given the numbers who appear to have slipped through the net, it is legitimate to ask: How many more people must die before we start to look more closely at the strategy of our intelligence services?” David Davies, a Conservative member of the British Parliament, wrote in the Guardian after The Post’s disclosure.

The revelation comes at a sensitive time in the British debate over whether its security services should be given even wider surveillance powers. There is no broad political support here for such a move, but Cameron has promised to beef up those powers should his Conservative Party win the next general election. In a recent poll, the pollster YouGov found that a majority of the British public support granting more powers to security agencies to fight terrorism, with qualifications.

Against the tide of public opinion swims Cage, a rights group that started as a Web site in 2003 and has sought to counsel young Muslims being monitored — and sometimes recruited — by British intelligence.

Qureshi cited Michael Adebolajo — a convert to Islam who, with an accomplice, hacked a British soldier to death in southeast London — as another example of someone who had been pushed further into the arms of extremism after coming under government “pressure.” The killer’s brother, Jeremiah Adebolajo, told Al Jazeera, “They began to harass him. They kept on calling him. They kept on asking him to meet. They kept on going to his house. He’s got family, he’s a family man. They were putting a lot of pressure on, really disrupting his life.”

Emwazi, a Kuwaiti-born British citizen in his 20s who grew up in West London and became a black-clad, blade-wielding, hostage killer in Islamic State videos, claimed similar tactics were used on him dating back to 2009, according to friends and e-mails he exchanged with Cage.

He and two friends traveled to Tanzania for what they said was a safari. But they were stopped and deported, leaving Emwazi to fly to Amsterdam, where he claimed that an officer from Britain’s domestic security agency, MI5, accused him of trying to reach Somalia, where the militant group al-Shabab operates in the south.

Map: Flow of foreign fighters to Syria

Emwazi stated that the British officer tried to recruit him, and, in subsequent e-mails, paints a portrait of continued pressure. In an e-mail exchange between Emwazi and Cage, dated June 2, 2010, he complains of being stopped by authorities from returning to Kuwait, where he had since found a job and a fiancee. He describes two British officials telling him he would be blocked from returning.

“One of them became aggressive with me, he pushed me against the wall,” Emwazi said in the e-mail. He said that the officials refused to identify themselves.

A spokeswoman for Britain’s Home Office said that “there is no confirmation or denying of any details around” the case.

As the threat posed by the Islamic State has increased, European nations have taken different approaches. Denmark, for instance, has treated returning fighters like wayward youths, seeking to find them jobs and send them back to school. Britain, though, has joined a growing list of European countries including Germany and France making terrorism-related arrests. Some nations are trying to stop potential homegrown jihadists before they board planes to the Middle East.

But if Qureshi argues that the government was too tough, others here are insisting it has not been tough enough. They question why and how Emwazi was able to leave Britain and travel to Syria after being repeatedly questioned since 2009. The British government, which has declined to confirm his identity, has not provided an answer.

Some critics have blamed a decision to do away with so-called “control orders” that once allowed British authorities to relocate suspects away from their homes as well as ban them from using mobile phones or the Internet. But critics have called such measures punishment without trial, and the government adopted a different set of still significant, if reduced, monitoring powers in 2011.

Alex Carlile, a Liberal Democrat in the House of Lords, told Sky News that if such rules had still been in place, Jihadi John “would not have done what he has done in recent times.”

Souad Mekhennet contributed to this report.