Anjem Choudary was “given the oxygen of publicity” by sections of the media and ideologues more interested in culture wars than fighting extremism, even as Muslims threw him out of their mosques, Britain’s biggest Islamic group said on Wednesday.

Choudary’s conviction for urging support for Islamic State has sparked debate and soul searching about how he spread his message inciting terrorism for so long before being charged and convicted of a serious criminal offence.

In a Guardian article, Miqdaad Versi, spokesperson for the Muslim Council of Britain (MCB) on security issues, said Choudary was given a platform to preach his pro-terrorist message by the media, not by Muslims. “His pulpit was not to be found in mosques but on the television screen and in national newspapers, ” he said.

The leader of the pro-violen ce extremist group al-Muhajiroun is believed to have influenced at least 100 people into terrorism. Versi added: “Choudary’s notoriety allowed him to reach the impressionable and vulnerable young people who felt alienated from the rest of society.”

The MCB is an umbrella group representing Islamic groups in Britain, but which has been shunned by government, which claims it has tolerated extremist views.

Versi said: “Choudary’s imprisonment is also a reminder of the shoddy state of counter-extremism in Britain. For years successive governments have struggled to define what extremism is and who they are trying to confront. Hasty and ill-thought-through measures have alienated the very Muslims who have kicked out extremists such as Choudary from their mosques.”

In his article Versi said confusion about what extremism is, plus an anti-Muslim agenda played a part in allowing Choudary to thrive. “The counter-extremism fight has become a casualty of an ongoing culture war pursued by ideologues with the ear of the government, bent on denying public space to Muslims who organise themselves,” Versi said.

“It is one that wrongly paints the life and practice of many Muslims as ‘conveyor-belts’ to violence with the assumption that the more conservative you are, the more prone you are to extremism.”

Police say for years they could not find sufficient evidence against Choudary despite his speaking out in favour of jihad, his refusal to condemn terrorist violence and his links to Britain’s most notorious terrorists and plots to kill.

Versi spoke out against the need for new laws but David Anderson QC, the independent reviewer of terrorism legislation, said experts would need to examine how Choudary got away with it for so long.

“One would have to admit that until now the law has barely touched Anjem Choudary,” he said. “In the meantime a lot of people have been radicalised and, yes, we do need to look at what might be done if there are impediments, technical reasons why it’s not as easy to get convictions under these laws as it should be.”

Anderson said it was “very difficult to craft a law that can clearly distinguish people who are dangerous from people who are simply revolting”.

He told BBC Radio: “It may be we need to be more clever than we already are in assembling evidence that can be used in a criminal court … The way forward is refining the application of the criminal law.”

Choudary, 49, and fellow al-Muhajiroun activist Mohammed Rahman, 33, face up to 10 years in jail for urging support for Isis via YouTube videos and will be sentenced in September.

Security officials are examining how best to neutralise Choudary’s disruptive effect behind bars and ensure he does not continue his activities in prison, which increasingly are believed to have become places of radicalisation.

Scotland Yard is also investigating Choudary’s wife over allegedly extreme remarks about Jewish people she made in a television documentary shown last year. Rubana Akhtar also said of Isis’s declaration of a caliphate: “The good days have already begun, nobody would ever have thought in our lifetime we would see the establishment of the Khilafah [Islamic state].”