Alan Titchmarsh, Percy Thrower and Diarmuid Gavin have all had the same issues, for work for B&Q, ICI and Westland respectively.
BBC editorial guidelines state: "It is essential that the integrity of BBC programmes or other editorial output is not undermined by the commercial, business or financial interests of presenters. In some cases, particularly for presenters of journalistic or factual programmes, commercial interests may be deemed incompatible with their on-air role."
Homebase representative Judith Ineson said: "We're working things out with the BBC. Joe can't refer to Homebase on the BBC but there is no problem in him getting involved in the garden."
Swift said: "I've always wanted to do a Chelsea garden but I've been too scared and I've not had enough time."