Questions over why some companies have copped an 'F' grade for ethics, despite not participating in the Tearfund ethical fashion guide.

More than 110 companies have received grades on their ethical fashion practices, with three of the five highest-rated brands from New Zealand.

While Icebreaker's come out on top with an A-plus, high fashion brand Trelise Cooper's hit rock bottom with an F.

Cooper herself claims she tried to participate - but was unable to meet an unreasonable deadline.

Tearfund chief executive Ian McInnes told Mike Hosking says it's not because she didn't take part - as the Warehouse still managed a C grade while opting out.

"You can, at rather bargain basement prices achieve a respectable grade and say 'look here these are my supplies and these are how we deal with my workers who make my garments.' "

 LISTEN ABOVE AS IAN MCINNES SPEAKS WITH MIKE HOSKING