Jihadis in Syria and Iraq from the U.K. should be encouraged to come home because a repenting individual may be able to shed light on the Islamic State, a former global counter-terrorism director told the Guardian.

Richard Barrett, a former counter-terrorism chief at MI5 and MI6, countered the strategy by Prime Minister David Cameron to ban British jihadis from returning home.

Cameron ordered passports of terrorist suspects to be seized, while London mayor Boris Johnson has said that the jihadis should have their citizenship revoked, The Guardian reported.

"(The fighters need) to know that there is a place for them back at home," Barrett said.

"These ex-fighters could help the authorities to understand better than they do now why people are still going to Syria and Iraq and what needs to be done to slow the flow to a trickle or stop it altogether."

His comments came after reports of disillusioned jihadis who wanted to detract but were afraid to.

"Many of the people who have been most successful in undermining the terrorist narrative are themselves ex-extremists. These are the people who can expose the true nature of the Islamic State and its leadership. Their stories of brutality and the motives behind it will be far more credible and persuasive than the rhetoric of men in suits." Barrett said.

Their experiences can help authorities get a better grip on the initial appeal of joining and using the experiences of detractors to fuel a deradicalization in the country.

Currently more than 500 citizens are believed to have gone to the Islamic State since 2011.

"These repentant fighters need a way out, and although the law must take its course, they need to know there is a place for them back at home if they are committed to a non-violent future," Barrett said.