The invention relates to a two component disinfectant composition comprising: (A) a peracetic acid-generating component comprising acetic acid, hydrogen peroxide and an organic phosphonic acid; and (B) a stabilizer component comprising an alkaline agent and a chelating agent, wherein the chelating agent is selected from the group consisting of N,N-bis(carboxymethyl)-L-glutamic acid, methylglycine diacetic acid, nitrilotriacetic acid, and alkali metal salts thereof, and a mixture of two or more thereof and to the aqueous disinfectant solution obtainable by mixing and diluting components (A) and (B) in water. The invention further relates to a method of disinfecting surface and instruments, particularly flexible endoscopes, using said aqueous disinfectant solution.