The Foundation calls for "a British Islam informed by British values"
The UK's mosques are out of touch with British Muslims and failing to root out extremism, a think tank has claimed.
The Quilliam Foundation, a group which opposes radical Islam, quotes a study saying 97% of imams were born abroad.
It says the lecture before Friday prayers in 44% of mosques is not in English, while nearly half have no women's facilities.
The Mosques and Imams National Advisory Board said the problem lay with outside groups "grooming" young Muslims.
Quilliam Foundation director, Maajid Nawaz, said the findings showed mosques lacked the "resilience to challenge Islamist extremists".
He described the statistics as "deeply disturbing", and warned that extremism could not be tackled while imams - mosques' religious preachers and educators - were "physically in Britain, but psychologically in Pakistan or Bangladesh".
He added: "Our first line of defence against terrorism is the ability, commitment, and confidence of mosques and Muslim communities to root out extremism.
"Currently, we are failing."
'Signs of hope'
The report argues that although mosques provide a range of services to their communities, many are led by a socially conservative older generation, out of touch with young British Muslims.
It says many foreign imams are low-paid and have limited proficiency in English, putting them at the mercy of management committees dominated by first-generation elders.
As a result, the Foundation says, imams are unable to reach out to young Muslims with "a British Islam informed by British values" - giving extremists the "upper hand".
The report's author, Anya Hart Dyke, said there were "signs of hope", however, with many mosques involving women and young people in their governance, sharing space with community organisations and opening their doors to non-Muslims.
"This needs to become the norm amongst our mosques," she said.
Seyyed Ferjani, chair of the Mosques and Imams National Advisory Board, told BBC Radio 4's Today programme there was a problem in the mosques, but not to the scale the report suggested.
"The imam in the mosque only leads prayers. We have a problem in our mosques that most, the bulk of our youth, they don't seek advice from imams, they seek advice elsewhere.
"And the problem that we've got, like the people who are in Leeds and elsewhere and groups here, they are outside of mosques, who are grooming them."
The Quilliam Foundation report comes the day after a Charity Commission study found mosques provided a range of community activities.
The Charity Commission study of 255 mosques in England and Wales was conducted by by BMG Research.
It found 94%, of mosques delivered educational programmes for children and young people, while 82% carry out fundraising for the relief of poverty and hardship.
The survey found 61% carry out women's groups and activities, while 47% deliver sports and leisure activities, and 31% organise activities for senior citizens.