The Prime Minister's wife wore an Alessandra Rich ankle-length lace dress and Zara court shoes.
"When I speak to buyers from other countries, they tell me that London is now an absolute 'must-have' city for fashion," Cameron told the Guardian.
Other celebrities in attendance at the Downing Street bash included Salma Hayek, Yasmin Le Bon, Manolo Blahnik and Donatella Versace.
The British Fashion Council turns 30 this year, with a new chairman Natalie Massenet at its helm.
In a speech at her inaugural launch, Massenet, the founder of Net-a-Porter, made her intentions clear, to foster British designers in London.
Best bits of London Fashion Week so far...
The big trends for AW13 are heritage fabrics, opulent sheepskin, leather and cashmere.
The first show to kick off London Fashion Week was Zoe Jordan, daughter of Formula 1 team owner Eddie Jordan.
She has used her experience as an investment banker to build a financially sound foundation for her label.
Her collection included evening wear and tailoring in black and grey wool. By popular consent, the most eye-catching piece in the collection was a tuxedo suit in metallic woven jacquard.
Hotly tipped to take Kate Moss's mantle as the UK's next supermodel, Cara Delevingne hit the runway on Saturday 16 February for Sister by Sibling's autumn/winter 2013 show.
Showing off the London trio's colourful knitwear, Delevingne stole the spotlight on the final parade of colourful winter warmers.
Bright and bold shades heralded the arrival of Jasper Conran's AW13 collection.
On a hot pink runway, models showed off dresses in neon orange, fuchsia and lime green.
Inspiration for Antipodium's autumn/winter 2013 collection came from Sharon Stone, Basic Instinct and 1990s glamour. Structuring took on a masculine edge, tailoring and bright splashes of colour in the trouser suits, jackets and shift dresses.
Pixie Lott joined Millie Mackintosh and Caroline Flack on the front row on Friday 15 February as they watched the Sass & Bide show.
The singer was wearing a frock with contrasting black trim, cutouts and front peplum ruffles.
Wearing her hair in a top knot - complete with a hint of pink dye - and glossy pink lipstick, her outfit was finished off with a clutch bag with cartoon motif.
This season a record numbers of buyers, including key representatives from influential American stores, are expected to attend London Fashion Week.
Tom Ford will be staging a full-scale catwalk show on Monday 17 February. Other anticipated shows include London debuts from L'Wren Scott and Rihanna, who will present her first 120-piece collection for River Island on Saturday evening.
There will be 56 catwalk shows by designers including Kane, Anderson, Jonathan Saunders and Simone Rocha, all of whom strengthen London's reputation for delivering the fashion stars of tomorrow.
On the front row
American Vogue editor Anna Wintour will definitely make an appearance at Christopher Kane. The label has just been bought by the Gucci group, so is one of fashion week's most sought-after tickets.
Alexa Chung and Pixie Geldof will stake out their seats for their friend Henry Holland's show. Chung is a big fan of Mulberry, who previously named one of their bestselling bags in her honour. As unofficial ambassador to the Mulberry brand, Kate Moss is tipped to be there too.
Beyoncé may well make a front row appearance. The bet is that she'll be spotted at Tom Ford's collection, as she previously modelled for the designer in one of his New York shows.