“If that isn't possible, more stock will be on our website next week. Sales of the tote bag anywhere else do not lead to a charity donation.”
The launch of the collection marked the Duchess’s return to royal duties some four months after the birth of her son, Archie.
She said the idea came to her after a visit to Smart Works, for which she is patron, when she realised that its donations were not necessarily the things women needed, such as a proliferation of lilac-coloured blazers.
The Duchess then personally approached the three “quintessentially British brands” to ask if they would create a capsule collection of workwear to be sold individually in the name of Smart Works while her designer friend Misha Nonoo contributed a crisp, white cotton shirt.
Miss Nonoo said on Friday that her friend “genuinely seeks to help people” and “really wants to make people’s lives better.”
She said the recent slew of criticism over various decisions made by Duke and Duchess of Sussex, such as their use of private jets whilst also urging people to reduce carbon emissions, was unfair.
"I think it's unjust, and I think that people should really focus on the good work they do,'' she told the Today show on US network NBC.
“A good example of that is this is her first official engagement after having had her baby (and) it's all about empowering women, all about what she has essentially always sought to do."
Miss Nonoo said the Duchess would be involved in several events focused on empowering women on the family’s official visit to South Africa next month.
The Smart Set collection is expected to be available for two weeks, providing enough stock for Smart Works to provide staple pieces to clients for a year.
The black and brown leather tote bags are being sold by John Lewis for £109 but are already being sold on eBay for up to £345.
The £19.50 Marks & Spencer dress, which has not sold out, is on sale online for up to £150, while the Jigsaw trousers, which are being sold at £120, are being hawked for £400.
Meanwhile, Smart Works revealed that the first clients to benefit from the project had been delighted to be given items from the collection after an initial “drop” was distributed to its centres across the UK.
One woman, identified only as Kate, said: “My outfit made me feel like a boss – powerful and strong. It just made me feel amazing, reminding me of how far I have come and the future I have in front of me.”
Supporters of the Duchess of Sussex have been urged not to buy sold-out items from her new fashion collection on eBay as a second wave of stock is imminent which will directly benefit the unemployed women the project was designed to help.
The back-to-work line, comprising five key pieces, was released on Thursday and was almost immediately put up for sale on the auction site at vastly inflated prices.
But the majority of the Smart Set collection remains available in most sizes via official partners including Marks and Spencer and Jigsaw, while the John Lewis leather tote bag, which quickly sold out online, will be restocked within days, the retailer said.
For every item from the collection purchased, one will be donated by the stores to the Smart Works charity, which in turn will give it to a woman struggling to get back into the workplace.
A John Lewis spokesperson said they were “delighted” with the success of the bag and that its focus was on the community-building aspect of the project.
They added: “For those customers who are interested in buying a bag and consequently having another one donated to Smart Works, we urge them to go into one of our shops where they can purchase a Smart Set bag today.