A process for the production of a polyether polyol, which is suitable for the production of flexible polyurethane foams, with an OH number of from 15 to 120 mg of KOH/g comprising: (a) introducing into a reactor or a reactor system a mixture of DMC catalyst and a poly(oxyalkylene) polyol, (b) continuously metering into the reactor or a reactor system containing the mixture introduced in (a) (i) at least one low molecular weight starter compound with a hydroxyl functionality of from 1.0 to 8.0 and a number-average molecular weight of from 18 to 1,000 g/mol, and (ii) a mixture comprising from 73 to 80 parts by weight of ethylene oxide per 100 parts by weight of (b)(ii) plus (b)(ii), and from 27 to 20 parts by weight of at least one substituted alkylene oxide per 100 parts by weight of (b)(ii) plus (b)(ii), the substituted alkylene oxide being a compound corresponding to Formula in which R1, R2, R3 and R4 independently of each other represent hydrogen, a C 1 -C 12 -alkyl group and/or a phenyl group, provided that: at least one of the radicals R1 to R4 does not represent hydrogen and one or more methylene groups in any C 1 -C 12 -alkyl radical may be replaced by an oxygen atom or a sulfur atom. (a) introducing into a reactor or a reactor system a mixture of DMC catalyst and a poly(oxyalkylene) polyol, (b) continuously metering into the reactor or a reactor system containing the mixture introduced in (a) (i) at least one low molecular weight starter compound with a hydroxyl functionality of from 1.0 to 8.0 and a number-average molecular weight of from 18 to 1,000 g/mol, and (ii) a mixture comprising from 73 to 80 parts by weight of ethylene oxide per 100 parts by weight of (b)(ii) plus (b)(ii), and from 27 to 20 parts by weight of at least one substituted alkylene oxide per 100 parts by weight of (b)(ii) plus (b)(ii), the substituted alkylene oxide being a compound corresponding to Formula in which R1, R2, R3 and R4 independently of each other represent hydrogen, a C 1 -C 12 -alkyl group and/or a phenyl group, provided that: at least one of the radicals R1 to R4 does not represent hydrogen and one or more methylene groups in any C 1 -C 12 -alkyl radical may be replaced by an oxygen atom or a sulfur atom. (i) at least one low molecular weight starter compound with a hydroxyl functionality of from 1.0 to 8.0 and a number-average molecular weight of from 18 to 1,000 g/mol, and (ii) a mixture comprising from 73 to 80 parts by weight of ethylene oxide per 100 parts by weight of (b)(ii) plus (b)(ii), and from 27 to 20 parts by weight of at least one substituted alkylene oxide per 100 parts by weight of (b)(ii) plus (b)(ii), the substituted alkylene oxide being a compound corresponding to Formula in which R1, R2, R3 and R4 independently of each other represent hydrogen, a C 1 -C 12 -alkyl group and/or a phenyl group, provided that: at least one of the radicals R1 to R4 does not represent hydrogen and one or more methylene groups in any C 1 -C 12 -alkyl radical may be replaced by an oxygen atom or a sulfur atom. from 73 to 80 parts by weight of ethylene oxide per 100 parts by weight of (b)(ii) plus (b)(ii), and from 27 to 20 parts by weight of at least one substituted alkylene oxide per 100 parts by weight of (b)(ii) plus (b)(ii), at least one of the radicals R1 to R4 does not represent hydrogen and one or more methylene groups in any C 1 -C 12 -alkyl radical may be replaced by an oxygen atom or a sulfur atom.