Pentecostal Christians outnumber Methodist churchgoers at services in England and Wales, research suggests.
About half of all Pentecostal churches are based in London
Sunday attendance at Pentecostal churches totaled 288,500 this year, compared with 278,700 at Methodist churches, it was estimated.
Manchester University's Dr David Voas, who studied English Church Census data, said Pentecostals were "the fastest growing group within Christianity".
He predicted they were third largest, behind Catholics and Anglicans.
Dr Voas said: "Methodism, a branch of Christianity that originated in England and spread around the world, is dying in Britain.
"By contrast, immigration from Africa and elsewhere has led to growth in Pentecostal churches, where the worship style is more flamboyant."
The forecasts were based on figures from the English Church Census, conducted by the independent charity Christian Research and sponsored by the Economic and Social Research Council.
Jonathan Kerry, co-ordinating secretary for worship and learning for the Methodist Church in Great Britain, said: "Methodism was born out of revival movements in the 18th Century and further renewal in the 19th.
"However, like many historic denominations, the Methodist Church now struggles to respond to new movements of God's spirit without feeling that it is betraying the past.
"Newer church movements, such as Pentecostalism - itself a century old - carry less of the weight of tradition, but typically also find themselves prone to similar challenges of stagnation or decline as the years go by."