Deputy Director Simon Calvert told The Telegraph, “Atheists are desperate - in their attempts to stamp out faith.”
The 24 places on Camp Quest UK, which will be held later this month near Bath, have already been booked up.
Organisers said the purpose of the camp was to encourage critical thinking and provide children with a summer camp “free of religious dogma”.
The camp, supported by God skeptic Professor Richard Dawkins, plans to expand after receiving hundreds of inquiries.
The event has been set up by Samantha Stein, 23, a postgraduate student of religion and contemporary society at King’s College London.
In an official Camp Quest UK Youtube channel, Stein said she was inspired to launch the camp after reading one of the footnotes of the book ‘The God Delusion’ authored by Prof Dawkins and attending Camp Quest USA in Michigan.
She said: “It is not about changing what they think, but the way that they think. There is very little that attacks religion; we are not a rival to religious camps.
“We exist as a secular alternative open to children from parents of all faiths and none,” she added.
According to the official website, the camp will include lessons on rational scepticism and moral philosophy, as well as traditional outdoor and music activities.
The sing-song will reportedly include John Lennon's Imagine, which contains the lyrics: “Imagine there's no heaven - it's easy if you try” and “No hell below us - above us only sky”.
The organisers said the theme this year would be evolution to coincide with the bicentenary of Darwin's birth and the 150th anniversary of the publication of On the Origin of Species. “The programme will also include canoeing, drama, nature hikes, singing and swimming. Cerebral pursuits range from talks on odd animals to a role-playing evolution game.”
The camp's launch follows the formation of the National Federation of Atheist, Humanist and Secular Student Societies (AHS) in March. The Federation is supported by Prof Dawkins and AC Grayling, Professor of Philosophy at Birkbeck College.
AHS plans to set up atheist societies in schools and universities across the UK to rival Christian groups. Also, next year Stein hopes to run atheist camps at Easter and during school half-term breaks.
Simon Calvert of the Christian Institute told The Telegraph, “Atheists are becoming increasingly militant in their desperate attempts to stamp out faith. It is deeply worrying that they now want to use children to attack the Christian ethos of their schools.”
“Many parents will be anxious at the thought of militant atheists targeting their children.”