The Girls Aloud singer, who was revealed last month as one of the celebrity models at during the biannual fashion spectacular, took part in a show featuring clothes from high street brands such as Warehouse, Forever 21, River Island and Dorothy Perkins at Westfield Stratford City.
According to ITN, Harding admitted that she was very nervous about her debut modelling gig and had been taking catwalk lessons in preparation for the event.
Alesha Dixon, Kimberly Wyatt and girlband Parade watched Harding walk down the catwalk in a tuxedo jacket and cropped trousers from the crowd.
The star was recently rumoured to have split from her fiancé Tom Crane after a series of rows, but the couple later said that they still hoped to go through with their wedding next April.
Crane said: "It's not over yet. We're just on a bit of a break. We were going through a rocky patch but when I come back from Ibiza we'll hopefully be able to get ourselves back on track."
Watch Girls Aloud's 'Call The Shots' video below: