The British model is expected to be responsible for the fashion and style section of the project that could double her fortune to 100-million-pound.
"She has been signed as a figurehead and style setter for the fashion end of the business. She will bring her expertise to the table, advising on all branding and style for clothes, hair and accessories," Contactmusic quoted a friend as telling Britain''s Daily Mail newspaper.
Her friend said: "She will also be involved in finding and signing new bands and promoting them. Something that has also been talked about is Kate developing her own singing career and starting a music label. She has a big network of people Philip and Simon have no access to and they want her to make the new venture hip."
Philip Green developed a business relation with the beauty after she signed up to create her own clothing range for his chain of British high street stores Topshop.
Kate"s pal added: "Philip knows Kate has been looking for a way out of modelling for the past five years. She's only confided in her closest friends because she still has outstanding contracts. No one knows she met up with Simon and Philip two weeks ago to sign and agree the final deal."