Kent County Council has rejected complaints of secrecy over plans for a new grammar school annexe in Sevenoaks.

The complaint came from the newly-established Kent Education Network, which is opposed to grammar schools.

It said KCC and the Department for Education had both rejected Freedom of Information requests concerning details and discussions around the plan because it was not in the public interest.

KCC has confirmed it holds information but is withholding it on the grounds it would prejudice the effective conduct of public affairs. It has not ruled out disclosure at a future time “when circumstances change.”

The Department for Education has also withheld information about the scheme but has also not ruled out the possibility that it might disclose it.

Joanne Bartley, chairwoman of Kent Education Network, said: “It ‘s disappointing KCC is keeping these plans to themselves. While parents were consulted in principle on this expansion, they want to know that their needs will be met. We believe that Sevenoaks parents should see the plan in detail and judge whether the annexe will meet their expectations.”

Kent County Council said it was not being secretive. A spokesman for the council said: “It is disappointing that Kent Education Network has quoted selectively from KCC’s response which reflected the language of the Freedom of Information Act.”

He added: “KCC has already provided relevant information in response to requests where it is able to do so. It would be unlawful to disclose some of the requested information and some specific information is either incomplete or cannot currently be disclosed where it would be likely to undermine the project.”

“Work is continuing on delivering the approved proposals and previous consultations have indicated high levels of public support for the project. Being unable to provide detailed particulars to a campaigning group for debate via the media does not amount to secrecy. Further detail will be provided about transport, staffing and other matters in due course.“

Opponents of the scheme had considered going to court to challenge the go-ahead for the annexe plan but did not, saying that it had not been given information from the government.

Education secretary Nicky Morgan has maintained the scheme complied with the legislation that permitted the expansion of over-subscribed popular schools and did not mean a return to grammar schools.