Foreign imams who do not learn English should be banned from giving sermons in UK mosques, a Labour peer has said.
The majority of imams speak Urdu as a first language
Lord Ahmed's comments come as a survey suggests imams lack professional and language skills to tackle the threat of radicalism among young British Muslims.
Only 8% of imams preaching in British mosques were born in the UK, it found.
Research at 300 mosques by Chester University for BBC News and the BBC Asian Network also indicated only 6% speak English as a first language.
The report acknowledges the use of English is becoming more prevalent at Friday sermons but says more investigation is required to assess the frequency and quality.
It concluded mosques often remained in the control of first generation migrants.
BBC religious affairs correspondent Robert Pigott says the survey does not contain evidence that imams are radicalising young British Muslims.
But he says imams face competition from groups who wait outside mosques to hand out leaflets and are prepared to talk to young people in English about issues such as discrimination and UK foreign policy in the Middle East.
Report author Professor Ron Geaves said its aim was to look at the ability of imams to adapt to modern Britain.
Lord Ahmed, who became the UK's first Muslim peer in 1998, said a new national advisory and training body was needed to train imams already in the country and impose bans on those who cannot speak English or understand the culture.
"They need to pass exams, they need to do more," he told BBC News 24.
"In fact, I would go as far as to say that if they don't learn English within a certain period then they shouldn't be allowed to deliver sermons."
Muslim leaders are meeting this weekend to discuss ways of tackling radicalism in their community.
Dr Usama Hasan, an academic and an imam in London, said some mosques did not "serve the needs" of Muslims who were born and brought up in the UK.
The general secretary of the Muslim Council of Britain, Muhammad Abdul Bari, said imams should be able to "talk and engage" people of all age groups.
"If they can play their role properly and communicate with young people they can get the message across to wider society in a very good way," he said.
Each mosque was asked a set of questions about imams including their place of birth, first language, qualifications and language of the Friday sermon.
The survey found 24 imams were born and educated in the UK, but this did not reflect the percentage of British-born South Asian Muslims who represent more than half of the Muslim population.
The survey found almost 45% of imams have been in the UK for less than five years.
The interviews conducted in February and March, also indicated that 50% of imams are from Pakistan, 20% from Bangladesh and 15% from India.
Some 66% of imams speak Urdu as a first language with 52% giving sermons in the language, it adds.
It also suggests that 6% of imams arrived in the UK in the past 12 months with 23% being in the UK for more than 10 years.
Professor Geaves said: "The study reveals a deeply conservative body of individuals maintaining traditional languages, types of qualification and still largely recruited from the place of origin."
The imams were "overwhelmingly" qualified in the traditional Islamic curriculum, which he said had changed little since medieval times.
He added: "Although there are social religious and political reasons that drive a need to transform the imamate to a 21st century British context there is as yet little sign of the mosque imams or their employers being ready to professionalise."