The sites in question includes part of Whitby Golf Club which is already owned and subsidised by the council and has struggled to remain financially viable as a sports facility. The council is believe to favour reducing the course from 18 holes to nine and selling off some of the land off Sandsend Road to a developer.
The other three parcels of land are on Rievaulx Road and at Spital Bridge.
The letter, published on the society's website, reads: "We understand that Scarborough Council is under external pressure to meet new homes targets and to generate new revenue; that there are few brownfield sites left in the town; and that a failure to find urban sites will mean further building on open land.
"Nevertheless, we believe that we should protect existing green spaces in the town. Even before the pandemic it was widely recognised that green spaces generate important benefits for health and wellbeing, and provide a valuable habitat for insects and bird life; they also aid water absorption and help mitigate flooding.
"The Local Plan emphasises the importance of green spaces, and Policy HC 14 sets out clear criteria derived from the NPPF which proposed redevelopment of green spaces must meet: 'Existing open space, sports and recreational buildings and land should not be built on unless (a) an assessment has been undertaken which has clearly shown the open space, buildings, or land to be surplus to requirements'.
"No such assessment is publicly available, and the council has not carried out a review of green spaces in the town since 2014. At that time its Green Space Audit found that Whitby was less well provided than elsewhere in the borough (we have 5.6 hectares per 1,000 inhabitants as compared with 7.4 hectares per 1,000 for the borough). There is then no evidence that existing green space is surplus to requirements.
"The legislative requirement to sell the land for the 'best possible price' will attract developers who are reluctant to deliver the promised levels of affordable homes. The benefits of density are lost when a high proportion is used for second homes or holiday lets, and past experience suggests that even where developers deliver the volume of affordable housing promised, there is at present no barrier to these being used as second homes or holiday lets.
"Three of the sites are designated local public green spaces and the authority is under a duty to protect them. The site at Spital Bridge forms part of an important corridor for wildlife; the two sites on Rievaulx Road are relatively small, but are valued by residents as they provide a space for children’s play, informal recreation, and dog walking. Further, the golf course land at Sandsend Road, while not defined as a public open space, provides much-valued sporting activities for club members and their guests.
"While Whitby Civic Society agrees on the need for additional affordable housing in Whitby, we very much doubt that there is a persuasive case for using these particular sites for development, and urge the council to protect these important open spaces for public use."
Scarborough Council has been contacted for comment.