Rod Stewart says song writing used to feel like school work.

The rock icon will release 'Time' - his first album of original songs in 20 years - next month and admitted writing his autobiography helped ignite a passion and ''pleasure'' he had never felt before, making the process much more enjoyable.

He said: ''My assumption was that I was finished as a songwriter. I was trapped down all sorts of unhelpful mental alleys.

''[But after writing the book] I was getting up in the middle of the night to write things down, which has never happened to me.

''I used to hate [song writing]. It was like being at school, 'Come on, Stewart, you've got to finish the lyrics!' - and you'd get kicked into a room with a bottle of wine. But this was just a pleasure and a joy. I loved every minute of it.''

Rather than laziness being the reason for not writing more songs, Rod revealed it is actually because he struggles with the process, sometimes spending days creating a ''rhyming line''.

He told the Daily Telegraph newspaper: ''I'll sing over some chords, searching, what does [the music] conjure up, where's the melody taking you?

''I deliberate over the lyrics, I really do. I'll come up with one line in a day, and then it might be a couple of days before I come up with the rhyming line. It's never been easy for me.''