All three singers are said to be worth £11m each in the study of music stars under 30 compiled by The Sunday Times.
It reveals that X Factor star Cheryl Cole more than doubled her wealth in 2009. Her personal fortune of £10m puts her in fourth place.
Cole's Girls Aloud bandmates come joint ninth, with £5m each. Craig David, on £8m, is the highest man at seventh.
Katie Melua ties with Cheryl Cole in fourth place, followed by Joss Stone, who is worth £9m.
Full list
Church, who has only recently stepped back into the spotlight, also held the top slot last year in the list of under 30s.
The classical singer, from Wales, launched a brief pop career in 2005, before moving into TV presenting and is now working as a judge on Andrew Lloyd Webber's TV show Over The Rainbow.
TOP 5 MUSIC EARNERS UNDER 30
1. Charlotte Church - £11m
1. Katherine Jenkins - £11m
1. Leona Lewis - £11m
4. Cheryl Cole - £10m
4. Katie Melua - £10m Source: The Sunday Times
Fellow Welsh singer Jenkins has also turned her attention to TV, recently appearing on the ITV show Popstar to Operastar.
Lewis, who has had two number one albums since winning X Factor in 2006, was placed sixth in last year's list.
Cole, who appeared at number 10 last year, boosted her fortune by signing up to be an X Factor judge.
She is also involved in several lucrative advertising campaigns, including L'Oreal, and released her debut solo album last October.
In a separate list looking at music millionaires of any age, Andrew Lloyd Webber, Sir Paul McCartney and Simon Fuller all feature in the top 10.
The list was topped by Edgar Bronfman, the chairman and chief executive of the Warner Music Group, who has a fortune of £1.6bn.
The full annual list of Britain and Ireland's richest people will be published on Sunday.
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http://news.bbc.co.uk/go/pr/fr/-/1/hi/entertainment/8638465.stm
