DORSET Wildlife Trust says it is disappointed that Studland is not to be included in the list of proposed Marine Conservation zones.
Defra proposes to designate only 31 of the 127 sites recommended by experts and stakeholders at the end of August last year.
The three Dorset sites included in the consultation are Poole Rocks in Poole Bay, Chesil & Stennis Ledges, home to rare pink seafans and native oysters and South Dorset, an area of mixed seabed habitats lying in deeper water.
Peter Tinsley, living seas manager at Dorset Wildlife Trust, said: "We are disappointed that promised coherent network of marine protected areas is not going to be delivered by designating such a small number of sites nationally. The network was designed to ensure that we don't end up with isolated and vulnerable sites and to ensure that the wide range of marine habitats found in UK seas are protected."
He added that the evidence and the ecological value of Studland was overwhelming and that DWT would be arguing strongly for its inclusion.
He concluded: "We accept that the site at Kimmeridge is too small to be viable and will argue that it should be increased, and we will push for the inclusion of the South of Portland site, which includes the extraordinary underwater cliffs of Portland Deep."