The three-times wed rocker - who has eight children with five women, including Alastair, seven, and Aiden, two, with his current spouse - insists he will stay with the blonde model ''for life'' and credits her with helping him out of low periods he has experienced.
He said: ''I feel the same about Penny today as I did when I met her 13 years ago. She's so sexy and she's my best friend.
''I do get down - I get my black dogs. But they don't last long as Penny digs me out of it.
''Like the other night, I had a bit of a sulk because I didn't really want to go out so she stood in front of me and started dancing. That's how she cheers me up. I said to her, 'You could've been the most expensive lap dancer in the world.'
''But she's everything to me - a great wife, a great mum and a great lover. And I'm with her for life.''
In recent years, Rod, 68, has grown increasingly close to his eldest daughter Sarah - who was raised by adoptive parents after he fathered her aged just 18 - and though it was difficult at first to create a bond, they now feel like ''family'' to one another.
Speaking about Sarah - who has no contact with her birth mother Susannah Boffey - he told The Sun newspaper: ''She's a great girl. I didn't change her nappies or do homework with her like I did my other kids, so at first it was hard to feel like my own.
''But I've worked hard at it and now it's beginning to feel like we're family.''