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The young open cluster Dolidze 25, in the direction of the GalacticAnticentre, has been attributed a very low metallicity, with typical abundancesbetween $-0.5$ and $-0.7$ dex below solar. We intend to derive accurate clusterparameters and accurate stellar abundances for some of its members. We haveobtained a large sample of intermediate- and high-resolution spectra for starsin and around Dolidze 25. We used the FASTWIND code to generate stellaratmosphere models to fit the observed spectra. We derive stellar parameters fora large number of OB stars in the area, and abundances of oxygen and siliconfor a number of stars with spectral types around B0. We measure low abundancesin stars of Dolidze 25. For the three stars with spectral types around B0, wefind $0.3$ dex (Si) and $0.5$ dex (O) below the values typical in the solarneighbourhood. These values, even though not as low as those given previously,confirm Dolidze 25 and the surrounding H II region Sh2-284 as the mostmetal-poor star-forming environment known in the Milky Way. We derive adistance $4.5\pm0.3\:$kpc to the cluster ($r_{\textrm{G}}\approx12.3\:$kpc).The cluster cannot be older than $\sim3\:$Myr, and likely is not much younger.One star in its immediate vicinity, sharing the same distance, has Si and Oabundances at most $0.15\:$dex below solar. The low abundances measured inDolidze 25 are compatible with currently accepted values for the slope of theGalactic metallicity gradient, if we take into account that variations of atleast $\pm0.15\:$dex are observed at a given radius. The area traditionallyidentified as Dolidze 25 is only a small part of a much larger star-formingregion that comprises the whole dust shell associated with Sh2-284 and verylikely several other smaller H II regions in its vicinity.

Open cluster Dolidze 25: Stellar parameters and the metallicity in the Galactic Anticentre