Mike Judge, a spokesman for the institute, said: 'All people should be free to change or modify their religious beliefs.
'That surely must be a core human right in any free society.
'I cannot imagine that an atheist foster carer would be struck off if a Christian child in her care stopped believing in God. This is the sort of double standard which Christians are facing in modern Britain.
'In recent months we have seen a nurse, adoption agencies, firemen, registrars, elderly care homes - and now a foster carer - being punished because of the Christian beliefs they hold. It has to stop.'