A sponge-forming liquid silicone rubber composition is provided. The composition generally maintains a stable emulsified state, can form a low-density silicone rubber sponge having a uniform and fine open-cell foam structure even when a coating or molding method involving shearing force and thin layer formation is used, is less likely to contract during curing, and that forms a silicone rubber sponge having a density close to the density designed on the basis of water content. A low-density silicone rubber sponge material using the sponge-forming liquid silicone rubber composition is also provided. The sponge-forming liquid silicone rubber composition comprises (A) an alkenyl group-containing organopolysiloxane, (B) an organopolysiloxane having a silicon atom-bonded hydrogen atom, (C) a mixture of water and an inorganic thickener, (D) an emulsifier, and (E) a hydrosilylation reaction catalyst. The contained amount of the component (C) in the entire composition is 70 mass % or more.