The present invention discloses a biocidal composition comprising hydrogen peroxide in a concentration of 0.05-50% (w/w) and a compound with a structure according to Formula 1: (OH)(X)(O)P--O--(CH--(Y)--CH.sub.2--O).sub.n--R, or a salt thereof, wherein X is H or OH, Y is H or CH.sub.3, n is 2-6 and R is an alkyl radical containing 4-18 carbon atoms, in a concentration of 0.01-60% (w/w). A especially preferred compound according to Formula 1 is a compound wherein X is OH, Y is H, n is 4 and R is a straight alkyl chain containing 10 carbon atoms.