Former Liberal leader Lord Steel has praised new Lib Dem leader Nick Clegg for his honesty in revealing that he does not believe in God.
Mr Clegg has been praised for giving a 'straight answer'
But Lord Steel - a practising Christian himself - said personal religious beliefs should be kept out of politics.
Mr Clegg, who was elected Lib Dem leader on Tuesday, was asked if he believed in God on BBC Radio 5 Live.
He replied 'no' but added later that he did not have a "closed mind" on the subject of faith.
He told the BBC News website: "I have enormous respect for people who have religious faith, I'm married to a Catholic and am committed to bringing my children up as Catholics.
"However, I myself am not an active believer, but the last thing I would do when talking or thinking about religion is approach it with a closed heart or a closed mind."
He did not elaborate further on his own beliefs, although school friends have recalled he was interested in transcendental meditation.
Mr Clegg's stance was praised by the Archbishop of Canterbury, Rowan Williams, who said: "It matters less to me than to know they are honest and reliable and that what beliefs they have they hold sincerely."
Lord Steel, who led the Liberal Party, as it was then known, from 1976 until its merger with the Social Democratic Party in 1988, said Mr Clegg had given a "straight answer to a straight question".
"I don't know Nick Clegg very well, but he is an engaging personality, highly motivated and dedicated, and you get what you see," the Lib Dem peer told BBC Radio 4's Today programme.
"He is very straight-talking. I think that is quite typical of him."
Lord Steel went on to say it was "not necessarily a good thing" that questions of personal religious belief had become a part of public life, particularly in the US.
"People who purport to be God's messenger on earth are a danger to politics.
"The problem in the world today is not Islamic fundamentalism, it's fundamentalism of every kind, Islamic, Christian or Zionist.
"I think it's best to keep religion as a private matter, not a public thing."
Lord Steel, whose father was the moderator of the General Assembly of the Church of Scotland, said his own Christian faith had been the "inspiration" for his political career "but that's not true of everybody".
Last month, former prime minister Tony Blair said he had not talked much about his faith for fear of being labelled a "nutter".
His ex-spokesman Alastair Campbell once told reporters: "We don't do God."
Current Prime Minister Gordon Brown, the son of a church minister, is also a Christian who has spoken of his father's advice acting as his "moral compass".