Nick Clegg has revealed he is not an atheist, as it is often claimed, and is 'open-minded' about whether God exists.

The Lib Dem leader is not a follower of any religion, although he said he 'dutifully' attends Mass every week with his Catholic wife Miriam and their three sons.

Mr Clegg was asked, during quick fire questions on the radio back in 2007, if he believed in God and he said 'no' but was not given the chance to elaborate.

But in an interview to be broadcast tonight, the Lib Dem leader claims he is not a 'rigid atheist' and although he does not follow a religion he has not ruled out the existence of God.

Nick Clegg is not a follower of any religion, although he said he 'dutifully' attends Mass every week with his Catholic wife Miriam and their three sons

Asked about his atheism, Mr Clegg said he wanted to correct the record and said: 'I'm actually not – and have never been – a rigid atheist. I was asked once, do I know whether God exists or not, and I'm actually quite agnostic. I don't know'.

Mr Clegg said as well as his wife, his Dutch mother and his brother are practising Catholics and he thinks 'it would be wonderful to be infused by faith' but that he is 'not a man of faith' and does not practice religion.

But he said: 'I very, very strongly believe we are spiritual beings. I also believe in the huge importance of it. I just happen not to be a sort of man of faith…So I'm not a practising Catholic but I would describe myself more as searching rather than being absolutely fixed in my certainties about what does or doesn't exist. And I like to think that's actually what most open-minded people are.'

He also revealed that the decision to bring his children up as Catholics was an order from his wife before they were even married, when they went to tell her local priest of their engagement.

He revealed that the decision to bring his children up as Catholics was an order from his wife (pictured) before they were even married, when they went to tell her local priest of their engagement

The Lib Dem leader's wife Miriam (pictured) has spoken of how her faith gave her comfort through dark times

'I remember when Miriam ushered me to meet the village priest in quite a rural part of Spain and she said, somewhat apologetically, 'Look, I want to marry this chap but he's not really sure what he is, religiously.'

'And this chap looked at me with a beady eye and said, 'I don't really care what he is, as long as he signs this piece of paper and ensures his children are educated as Catholics.' I said, 'Well, hang on a minute,' and Miriam said, 'Sign the piece of paper!' (Laughter) And at that moment, the spiritual existence of my then unborn children was determined.'

Miriam has spoken of how her faith gave her comfort through dark times. Mr Clegg said when his eldest son was critically ill, he 'longed' for his recovery but did not pray 'in the conventional sense.'

He added during the interview that despite the stresses of the campaign he had finally quit smoking, and goes to the gym every week to do kick-boxing. He once the sport helps him 'get stuff out of my system'.

But as to who he imagines while punching the bag, he said: 'Well, sometimes Ed Balls might flicker through my imagination.'