The company's on-pack promotion offers consumers 20p off their next purchase, while money-off coupons will run in 15 publications, including The Radio Times, and vouchers will be door-dropped to 2.2m households.
Hovis reports that 400g loaves are predominantly bought by consumers from one- and two-person households, with 80% of the spend coming from consumers who are 45 and over.
Edward Milner, Hovis head of category management, said: "The 400g category is a crucial part of the bread market. Due to changes in consumption and household demographics, it has been in growth for many years. For a large proportion of the country, 400g is more relevant than a larger loaf, so it is important that we provide for them."