Suffolk County Council has waded into the row over controversial plans for 400 homes in west Suffolk after urging its district counterpart to consider the wider context.

The county council has penned a lengthy letter to Forest Heath in the latest twist to the saga over Hatchfield Farm in Newmarket.

The main thrust of the letter surrounds Forest Heath having to decide the application without a confirmed local plan, which is in the process of being finalised.

Its core strategy had to be thrown out in 2011 after its provision for Hatchfield Farm was successfully challenged in the High Court.

The letter also questions the development’s impact on the horse racing industry, as well as traffic and school places.

Suffolk County councillor for the area, Lisa Chambers, said: “Newmarket is a unique town with very specific needs.

“These include the yet to be finalised requirement for more housing, but also the imperative to make sure the area remains attractive to the horse racing industry, on which so many people rely for work.

“This development will create the need for at least 100 additional primary school places but, in the absence of an adopted local plan and a suitable identified site for a new school, it becomes harder to ensure that proper provision will be made.

“This is a critical issue in any large-scale development and must be looked at carefully before any development is considered.”

Proposals for 1,200 homes at Hatchfield Farm were rejected by Forest Heath in 2010, and by a planning inspector in 2012 after an appeal by applicant Lord Derby.

A recent independent report found the horse racing industry supports around 3,285 full-time equivalent jobs within 25 miles of Newmarket, and contributes more than £200 million to the economy.

Rebekah Paczek, a spokeswoman for Hatchfield Farm, said the reduced application had come about after extensive consultation with more than 200 people at a public exhibition and 100 through on-street surveys.

She added: “The Economic Impact of Horseracing Report paints a picture of a thriving and growing industry and not one which would be adversely affected by 400 dwellings at Hatchfield Farm.

“Through working together we can bring forward positive development which support the horse-racing industry, infrastructure and the requirements of the wider Newmarket community.”

She also pointed to the former St Felix Middle School site, in Fordham Road, as a “ready-made school site”, adding: “Suffolk County Council should be planning for a new primary school on this well-located site using contributions from new development, such as Hatchfield Farm.”

Richard Smith, county council cabinet member for economic development, planning and environment, said: “The county council believes that to do our best by Newmarket, and to ensure that the town remains attractive to the horse racing industry, the local plan offers our best opportunity for managing new development.

“It is therefore disappointing that Forest Heath is being asked to consider this development in isolation and on an ad hoc basis.”

Allocating sites for housing in Newmarket proved a major sticking point in discussions by Forest Heath’s local plan working group late last year.

Hatchfield Farm was allocated 700 homes as part of Newmarket’s quota, but the final allocation remains far from decided.

A Forest Heath spokeswoman said: “Suffolk County Council is a consultee on all our planning applications and their comments will be considered by the Development Control Committee, along with responses from other organisations and individuals, before any decision is made.”