Nicky Gumbel from Holy Trinity Brompton said teaching by the Parachristo group - based in the Docklands area - is "deceptive".
In an email seen by the Daily Telegraph, he and his wife, Pippa, wrote: "'ParaChristo' is connected to a South Korean cult called Shincheonji led by Leen Man-hee.
"As followers become more dedicated, they are taught that Lee Man-hee is the 'Advocate' and 'new John' who is to be worshipped.
The Anglican priest and author went on to say: "We are now in contact with other churches who have experience of this deceptive and potentially dangerous cult."
According to the Daily Telegraph, concerns over the Parachristo group has also sparked a formal alert from the Diocese of London to its parishes across the capital.
A lawyer for Parachristo told the newspaper: "Parachristo was set up by members of New Heaven and New Earth (Shinchonji) to teach God's revealed word through the Bible to people."