The DRC has commissioned the BSI to produce new guidance [which] will take the aim of informing website commissioners and developers of their obligations and of good practice in [the area of web accessibility]. This guidance takes the form of a Publicly Available Specification (PAS). [...] A PAS is not a full British Standard but is developed using the same rigorous processes. [...] PAS 78: Guide to good practice in designing accessible websites will remind web developers of the vital importance of web standards. [...] It is due to be published this Autumn.
See the full press release from the DRC: Making websites accessible - new guidance planned. Hat tip to Julie Howell from the RNIB.