A decision on plans for 450 new homes in south-west Chippenham is being held up by negotiations over the proportion of affordable housing.

Wiltshire Council was due to make a decision today on the proposed Hunters Moon development, which comprises 11 fields bordered by West Cepen Way, Easton Lane and Saltersford Lane.

But developer Bloor Homes said yesterday it was still in negotiation about the percentage of affordable housing.

It had proposed 30 per cent, which would mean 135 homes, but the council was pushing for 40 per cent, or 180 homes, after its new housing team advised there were 1,069 households seeking affordable homes in Chippenham. Councillors said plans also needed to provide bungalows to meet the needs of an ageing population.

Bloor Homes planning manager Mike Kerton said the company was assessing whether it could meet the requests, and that including bungalows in the project would depend on demand.

The outline application, which includes a primary school and an employment area of about 2.3 hectares, is now likely to be heard by the northern area planning committee next month, along with a full application for an immediate first phase of 103 homes and 10 business starter units at the top of the site.

Residents fear the green buffer between Chippenham and Corsham will be lost if Bloor Homes is given the green light to build on the 30-hectare site near Methuen Park.

Wiltshire Council received objections from four members of the public during consultation, which ended at the start of August. Corsham Town Council recommended rejecting the plans on the grounds that “brownfield sites should be developed first” and building would impinge on the green buffer.

Paul and Kirsty Martin, residents of Old Thingley Lane, agreed: “It’s the start of a slippery slope that will see the diminution of the individual character of both settlements.”

Mr Kerton said the plan would provide more open space than required – about 10.4 hectares, to include a central hilltop park and multi-use games area.

He said: “The location and nature of Hunters Moon means we are able to deliver much-needed new homes and employment space for Chippenham, without compromising areas of high grade agricultural land, disturbing local wildlife reserves or relying on complicated infrastructure requirements to make it deliverable.”

Neighbour Janet Nuthall wrote to the council: “The transport and roads infrastructure cannot cope with demand. Traffic is already a nightmare around the Sainsbury’s and Pheasant roundabouts.”

She also questioned the demand for business development. “There are a large number of vacant units in Bumper’s Farm and the Methuen estate,” she said.