But he stressed that while Ukip will stand up for Christian values that does not mean it should require people to hold a certain faith.
His intervention comes weeks after a social attitudes survey found that Britain is becoming an increasingly godless society, with more than half of the population now describing themselves as having "no religion".
Mr Crowther told Ukip's party conference: "Our society has been built on Christian principles, including the primary aspirations to be loving, forgiving, peaceful and just."
He went on: "But including Christian in our list [of principles] does not imply any requirement for individual faith, but it reflects the Judeo-Christian classical and enlightenment origins on which our laws, our social systems and our cultural norms have been built over two millennia.
"We are a Christian country and we intend to stay that way."
UKIP are set to replace Steve Crowther tonight with a permanent leader.
Anne Marie Waters, one of two candidates, has previously described Islam as "evil", leading to several members saying they will leave the party if she wins.
She founded Sharia Watch UK, which seeks to document the 'advancement' of sharia law and the methods of its so-called advancement.
Former leader Nigel Farage has warned Ukip will be "finished" if it becomes anti-Islam, although he has denied reports that he will quit to spearhead a new movement if Ms Waters is elected.