The MasterChef star, 60, stepped down from the programme five months ago while complaints from 13 women about historical allegations of misconduct were investigated.
One-time grocer Wallace, 60, stepped away from the show in the wake of a number of allegations that he had indulged in sexist banter and harassed contestants. He denies any wrongdoing.
The former MasterChef host, 60, stepped down from hosting the show with Jon Torode in November after multiple complaints of inappropriate behaviour on set.
Masterchef's production company has hired law - Lwis Silkin - firm as a series of women are interviewed as the investigation into the TV chef's behaviour officially begins.