UP to £4m of taxpayers’ money could be spent securing land for a controversial free school, it has emerged.

Education chiefs are considering two permanent sites for Durham Free School (DFS) and although ministers refused to disclose locations, it is believed the cost could be close to £4m even before any building begins.

Durham City Labour MP Roberta Blackman-Woods, who has demanded the school’s closure, said the information strengthened her long-standing claim it was a total waste of money.

But John Denning, the chairman of governors, said DFS, which opened in the former Durham Gilesgate Sports College temporarily last September, was already a great success and its costs were modest compared to other new County Durham academies.

The school has become a focus of the national free school debate, with Labour claiming it has cost more than £25,000 per pupil and Education Secretary Michael Gove repeatedly defending it.

School leaders have always wanted to be south-east of Durham City and in a letter to Dr Blackman-Woods schools minister Lord Nash confirms two permanent sites are being “assessed” but refuses to name them, claiming this could “weaken our negotiation position with landowners”.

He says there would have to be around 59,000sq ft of floor space, which would typically mean a seven-acre site – and one North-East property expert said land around Durham City would cost at least £500,000 per acre.

Alternatively, the school could be placed on a smaller or leased site.

Dr Blackman-Woods attacked the secrecy of the process, which is led by a Department for Education agency.

DFS currently has about 37 pupils, which is expected to grow to 90 by September; although leaders admit uncertainty over the site has hit parents’ confidence.

Nevertheless, Mr Denning said he was absolutely delighted with the school’s work to date and parents were very happy.

He added DFS has the same funding formula as all state schools and said its costs were modest compared to new academies set up in Consett and Stanley, which he put at £43m and £30m respectively.

Three bids for potential permanent DFS sites fell through last year and the school is expected to remain in Gilesgate until at least summer 2015.