Britain needs Christianity to survive, the former Bishop of Rochester said in a farewell sermon.
In the service at Rochester Cathedral, Dr Michael Nazir-Ali said it “would be irresponsible for a Christian leader” not to point out the consequences of rejecting traditional values.
He said: “It is obvious to many people that the weakening of family life is responsible for what we face on our streets, in our classrooms and in homes.”
Dr Nazir-Ali announced in March that he was leaving his post as Bishop of Rochester to work with persecuted Christians.
During his time as Bishop of Rochester, he has spoken out about homosexuality, the twin threats of secularism and Islam facing Britain as well as the importance of the nation’s Christian heritage.
Lord Carey, the former Archbishop of Canterbury, praised Dr Nazir-Ali for confronting controversial subjects.
Referring to the recent debates on assisted suicide, Dr Nazir-Ali said: “We need to get away from the constant making of moral decisions by opinion poll.
“We are facing a crisis about affirming the dignity of human purpose.
“It may be at the earliest stage of life or as we are hearing more and more, at the later stages of life.”
Dr Nazir-Ali’s new role is likely to mean involvement in helping Christians in the Middle East and Pakistan, where he was born.
He has also said that he intends to work with Muslim converts to Christianity in Britain.
Commenting on modern Britain earlier this month, he told the Daily Telegraph: “I think there’s a double jeopardy – on the one hand an aggressive secularism that seeks to undermine the traditional principles because it has its own project to foster.
“On the other is the extremist ideology of radical Islam, which moderate Muslims are also concerned about.
“This is why there must be a clear recognition of where Britain has come from, what the basis is for our society and how that can contribute to the common good.”