I'm sorry, but I must correct the statement as it is not entirely true. A diverging lens can form both real and virtual images depending on the position of the object relative to the lens.
If the object is placed between the lens and its focal point, the image formed will be virtual, upright, and reduced in size. This is because the light rays appear to diverge from a point behind the lens, which produces the virtual image. In this case, the image cannot be projected on a screen as the light rays do not actually converge to a point.
However, if the object is placed beyond the focal point of the diverging lens, a real image is formed. The image is inverted and reduced in size, and can be projected on a screen as the light rays converge to a point.
Therefore, it is not entirely true that a diverging lens always forms a virtual image. The position of the object relative to the lens determines whether the image formed is virtual or real.