Nick Lachey has a ''mutual respect'' for his ex-wife Jessica Simpson.

The 46-year-old star - who was married to Jessica from 2002 until 2006 - is one of the subjects in Jessica's new memoir 'Open Book', and has said that whilst he hasn't yet read her book, he has nothing but the utmost respect for his former flame.

Nick - who is now married to Vanessa Lachey - told the 'Today' show: ''I haven't read the book so I don't know what she said or what she revealed but certainly happy for her in her life and I know she is happy for us. There is definitely a mutual respect there. Obviously, it was a long time ago and we've all moved on.''

The former 98 Degrees singer mirrored his comments in an earlier interview, where he stated neither he or Vanessa had read the tome.

He said: ''Well, no, I have not read a single word. Both of us have not read the book, and no, she did not reach out before it was published.''

In her new book, Jessica, 39, described Nick as her ''first love''.

The blonde beauty - who previously admitted being a virgin before their marriage - wrote in her book: ''Nick loved the fact I was so strong in my faith and that I had this wide-eyed innocent approach to life. When he proposed in 2002, I said yes.''

And despite their much-discussed split, Jessica has also insisted she remains respectful of her ex-husband.

Jessica - who has been married for former gridiron star Eric Johnson since 2014 - said: ''I was really young and my success hadn't really begun.

''He knew me as this young, innocent 18-year-old that had never been introduced to the world in so many ways. I went straight from my father to him. Nick's very smart. He was eight years older than me, but he was also young.

''We meant a lot to each other and we always will. I want to be very respectful because I married him for a reason and we were together for seven years for a reason. He has a family now and I would never say anything to disrespect that.''