PURPOSE: To obtain a polyester material for producing spun fibers providing a polyester having high whiteness and low yellowness as compared with a conventional method.

CONSTITUTION: In a method for producing a low combustible linear polyester having enhanced whiteness and reduced yellowness by forming bisdiol ester or its oligomer by the esterification of an aromatic dicarboxylic acid or the transesterification of its bis(lower alkyl)ester with or without an aliphatic dicarboxylic acid with diol and condensing these preproducts to obtain spinnable polyester, 0.5-15 wt.% of a phosphorus-containing modifier is added to the esterification, transesterification or polycondensation batch and polycondensation is executed initially in the melt to an intrisic viscosity from 0.4 to 0.55 dl/g and thereafter in a solid phase to an intrinsic viscosity from 0.62-0.72 dl/g (inherent viscosity is measured in dichloroacetic acid at 25°C).