The founders of a Christian-ethos free school have resigned as trustees, citing anger at the government’s “lack of protection” for the institution’s religious character.

Elizabeth Gray and John Burn have stepped away from the Grindon Hall Christian school in Sunderland as a lengthy takeover by the Bright Tribe academy trust nears its conclusion.

The pair say they had no choice but to resign because Grindon Hall, which Gray founded as an independent school nearly 30 years ago, before it converted into a free school in 2012, will lose its Christian ethos.

Burn, a former headteacher and member of the National Curriculum Council, told Schools Week: “Bright Tribe is not a Christian body, it’s a secular body, and it’s ridiculous to expect a secular body to manage a Christian school.”

He said the school did not have the same government protection given to those that formally belonged to the Church of England or Catholic church.

It’s ridiculous to expect a secular body to manage a Christian school

“The Anglican schools are protected,” Burn said. “We’re a non-denominational Christian school, and we think we should be in the same position as the Anglican and Roman Catholic schools.”

In the government’s education white paper, a memorandum of understanding (MOU) was established between the Department for Education (DfE) and the Church of England and Catholic church.

It promised the churches could “expect their academies to remain part of a diocesan family of schools” and the “religious character and ethos of church and faith schools be protected” should they be taken over by a new trust.

The MOU also states that church academies must demonstrate a “broad and balanced curriculum that prepares pupils for life in modern Britain” – the strongest area of criticism against Grindon Hall in Ofsted’s 2014 report.

The free school was put in special measures after the inspection, which found students showed “a lack of respect and tolerance towards those of different faiths, cultures or communities”, while safeguarding procedures, recruitment processes and academic progress in writing skills were also insufficient. Inspectors have since told the school that it is making good progress.

Bright Tribe is still to take over the school, with the lengthy delay calling into question the government’s claim that academisation allows ministers to remove schools quickly from under-performing providers.

However, the trust this month put out an advert for a new principal at Grindon that said the new head would “lead the successful development and implementation of the school’s Christian ethos”.

Bright Tribe, which runs 12 schools, is also at the centre of a financial storm after Schools Week revealed that the government was refusing to publish an investigation into payments it made to companies connected to its founder Michael Dwan, despite the regular publication of similar investigations into other trusts.

A spokesperson for Bright Tribe said: “The school is designated as having a faith character and the trust is committed to ensuring that the Christian ethos is maintained.”

Meanwhile in the north east, the Church of England is set to take over four non-religious schools – a move humanist organisations have called a “deeply anti-secular development”.