Kent County Council has changed its stance on a controversial planning application to build 180 homes on school playing fields, with a new decision to oppose the bid at appeal.

The county, which raised no objections on highways grounds, when the proposal to build on the New Line Learning grounds off Boughton Lane in Maidstone was first raised in February 2014 has now concluded that the scheme would cause “severe congestion” on the Loose Road and must be opposed.

Barbara Cooper, the county’s corporate director for transport, has written to the Department of Communities and Local Government to say: “The cumulative impact of recently completed or consented development along the A229 Loose Road and the A274 Sutton Road corridors will lead to an unacceptably severe impact on the local highway network without there being sufficient certainty that strategic mitigation can be provided and funded.”

She said: “A piecemeal approach to create further capacity at the Swan junction in isolation is unlikely to be appropriate in view of the cumulative effects of additional traffic on congestion across the wider network.”

The new approach, which KCC said was because it now had the result of a traffic modelling exercise that had not previously been available, will put it on a collision path with Maidstone council.

The borough’s planning officers have included the Boughton Lane site among those in its draft Local Plan proposals, albeit for a smaller number of 120 homes.

The borough commissioned its own traffic consultants to suggest ways of modifying the crossroads at The Swan pub so that the harmful impact of the increased traffic could be mitigated.

Mott MacDonald suggested there was just one option available: allowing traffic from both Cripple Street and Boughton Lane to proceed across the junction at the same time. That suggestion has been condemned as dangerous by the local county councillor Ian Chittenden (Lib Dem).

He said: “Traffic lights were first introduced into this junction because of safety concerns and a record of accidents.

“The proposal made by Mott MacDonald is unworkable and unsafe. No safety audits have been carried out to support the proposal from Mott MacDonald.”

The appeal inspector has allowed a three-week delay in the appeal timetable to allow the applicants, BDW Trading, time to respond to the new developments.