Dame Vivienne Westwood has urged the Duchess of Cambridge to stop buying so many different outfits - and make more of an effort to be environmentally-friendly.
Before her London Fashion Week showcase at the Saatchi Gallery, Dame Vivienne said that when Kate goes to so much effort to get an outfit that looks good, she should wear it more often.
The fashion icon, who believes in quality over quantity, disapproves of the duchess's expansive wardrobe.
She said: "I don't have any advice to her, except I think it would be great if she wore the same clothes over and again, because that's very good for the environment and it would send out a very nice message.
"If you're going to all that trouble to get an outfit that suits you, then you should keep on wearing it.
"I mean you don't have to have a red outfit one day and then something almost the same in blue the next."
Westwood, dressed in her usual wacky style with an image of Julian Assange on her T-shirt, said her Red Label collection also carried the theme of quality over quantity - but did not mean less glamour.
She insisted: "It's for anybody that wants to dress up quite wonderfully glamorous.
"All I can say is it's quite a short collection this time because what I'm trying to aim for in my second line and all my offshoot products is to just keep aiming for quality all the time and have less quantity.
"I'm just trying to do a quality choice for people to wear something that really helps them to look good.
"That's what fashion is here for. It's here to help," she said.
However, after his showcase in Covent Garden's Royal Opera House, designer Matthew Williamson expressed his opposition to Westwood's comments on Kate, who has been pictured wearing his designs.
"She has a lot to do doesn't she? So she needs a good wardrobe. So, no, I disagree," he said.
When asked if a woman can ever have too many clothes, Williamson said: "Of course not."
The Westwood and Williamson shows were two of the most eagerly anticipated events on day three of the fashion extravaganza.
This year's Fashion Week is featuring 56 catwalk shows and 20 presentations.
More than 120 UK and international, emerging and established, ready-to-wear and accessory designers are taking part.