Nganga spent 19 years as a 'fervent evangelist' after converting in 1989 and devoted his life to the bible and abstaining from sex. He is now suing the leaders of the Baptist Union of Great Britain, who, he says "conspired to defraud me of my finances, time and my life".
Nganga filed papers in the high court accusing the church of destroying his social life, causing him 'psychological harm' and defrauding him of money through compulsory donations.
He blames the church leaders for physical assaults suffered at the hands of those he was trying to convert.
"They got upset and reacted violently after being told that they were sinners. I was slapped and punched, and kicked in my left knee, breaking its cartilage."
The church said last week that it would vigorously contest the claim. As well as suing the British arm, Mr Nganga has begun a legal battle with the US-based Baptist World Alliance and has written a book, The Millenary Fraud.