According to a newspaper investigation, workers at the plant in Dongguan earn 1 a day and sleep in crowded dormitories.
Mone, the Glasgow-based businesswoman behind the Ultimo brand, insisted the facility in southern China, where clothing for other leading high-street brands is made, was no "sweat shop".
The Daily Record said the plant’s 800 workers were prevented by guards from leaving during work hours and received just two weeks’ holiday a year. The women who manufacture the Ultimo bras, which retail for about 25 each, work six days a week for 33 a month, claimed the report.
But the MJM founder said: "The factories we use for production of our garments fully comply with local government regulations.
"In addition to this, we and all our customers have our own strict guidelines in which to operate. We visit our factories on a regular basis.
"We don’t and have never used sweat shops, even though we could make more profits if we were manufacturing in sweat shops."
Ms Mone, 34, who was branded "nasty" by Rod Stewart after she replaced the singer’s girlfriend, Penny Lancaster, with his ex-wife, Rachel Hunter, to model Ultimo’s range, said she was fed up of criticism.
"This is just wearing me down, I’m trying to create jobs in Scotland and create a worldwide brand in Scotland and this is what you get," she said.