"Seven years ago, the last factory closed, so we were no longer able to access the machinery we needed, so we went offshore," she said.
"Before we did this, we used a New Zealand company and we wanted all the accreditations met by us before we went ahead and we were assured that they do not use child labour.
"People work 40-hour weeks, they get lunch breaks and they're treated no differently to our New Zealand employees. We're not the sort of brand that is going to go in blind and just do this."
She said the issue would become more pronounced as more local factories closed down, with fashion retailers taking their production abroad.
"We actually stopped the production of denim jeans and jackets because we could not get them made in New Zealand any longer. We made a decision to stop a very profitable part of the business because we didn't want to take it offshore."
Asked whether the "made in New Zealand" tags on the clothing at World might have created some confusion among shoppers, L'estrange Corbet said it didn't.
"The tags are made in New Zealand. The fact that the garments aren't made in New Zealand is very clear on the garments."
She was reluctant to change her "Made in New Zealand" swing tag because the origin of the garment was clearly visible on the neck tag.
"I don't think it's misleading, but if anyone thinks it is then I can cut that bit off."
L'Estrange Corbet said that discouraging reports such as these made her question her commitment to New Zealand, saying she didn't have to do it.
"I don't have to support people here, I don't have to give anything back, but I do it because I want to give back."
L'Estrange-Corbet was made a dame for services to fashion at the end of last year, and has long been a critic of overseas manufacturing.
Ben Kepes, owner of Cactus Outdoor, a Christchurch-based outdoor clothing company, said it was still possible to make T-shirts in New Zealand.
He said his firm has been working to promote its 25 years of manufacturing garments in New Zealand, using social media to show exactly where and who is making the clothes.