The former head designer of Michelle Mone's lingerie company is taking it to an industrial tribunal amid claims she was forced to quit because of her "erratic and irrational" boss.

Helen Graham, 32, will tell an employment hearing next week that in her nine months at MJM International, famous for its Ultimo bra, she was subjected to "serious unjustified, ill-tempered and irrational personal and professional criticism".

She is now suing Scotland-based MJM for breach of contract and three months’ pay. She claims the final straw was her employer’s reaction to a magazine interview she gave in which she claimed Mrs Mone was not a designer.

Mrs Mone today denied the claims and added: "The application is being vigorously opposed."