The present invention is a laundry detergent booster liquid composition comprising from about 0.3% to about 7% of a soluble alkali metal carbonate, especially sodium carbonate in an aqueous solution. The booster liquid formulation may contain additional laundry detergent additive materials such as thickening agents, optical brighteners, anti-redeposition agents, surfactants, phosphates, dyes, and fragrances in addition to the alkali metal carbonate.