Britney Spears is ''shy, but fierce'' according to will.iam.

The Black Eyed Peas star worked as executive producer on the 'Work Bitch' singer's latest album, 'Britney Jean', and says he thinks she is the most ''focused and disciplined'' singer around.

He told ''I like Britney. I just love her dedication and love for music. That's just the way it is. I love how sweet she is, and how genuine she is. Shy, but fierce.

''Most artists aren't like that. I don't want to name artists but Britney is the most focused and disciplined of all the artists in the industry.'' went on to explain how hardworking Britney is in the studio and how she is always professional when laying down tracks.

He said: ''Britney's a pro. Her time is valuable: She has kids. And a lot of the time with an artist they'll go into the studio, they'll sit around, they're watching TV, they order some food, they're giggling and joking, they're searching and listening to other people's songs ... Britney's like: 'I'm coming in from 2pm until 6pm.' She'll arrive at 1.30, and from 2 to 6 she'll be like BAM BAM BAM BAM BAM BAM. BAM BAM BAM BAM. BAM BAM. I've never seen anything like that. Her work ethic is pretty admirable.''

'Britney Jean' is released today (29.11.13).