Government plans to combat religious extremism by strengthening independent-schools’ standards in the wake of the alleged Trojan Horse plot have been branded “unlawful” by a Christian charity.

The Christian Institute is threatening the government with a judicial review following its proposals to bolster standards in independent, academy and free schools to ensure they “promote British values”.

It comes two months after the Church of England’s new head of education warned that schools should not be forced to remove “all references to religion” in the aftermath of Trojan Horse. 

A consultation on the new measures was announced in June at the height of the Trojan Horse affair, in which a group of schools in Birmingham were found to have fallen under the influence of Islamic extremists.

But the institute has concerns that the measures will have perverse consequences that will force independent schools to downgrade religious festivals, such as Christmas, so as not to offend atheists and those of other faiths.

It also claimed that, under the new guidelines, schools will be prevented from using gender specific terms, such as husband and wife.

As a result, the group has engaged lawyers and is threatening the Department for Education with a judicial review on the basis that the six-week consultation process was flawed and broke the government’s own guidance.

In a letter to the department, lawyers for the institute wrote: “It would be unlawful for you to proceed on your current timetable for the closing of the consultation and the implementation of the subsequent amended standards and associated policy matters consulted on.”

According to the charity, the department insisted it was “confident” it had allowed “sufficient time for stakeholders to make representations” and pointed out that around 30 schools had submitted responses by the end of last month.

But the institute dismissed this as inadequate, saying they represented less than 0.5 per cent of the total number of schools affected directly.

Colin Hart, chief executive of the institute, said it was a “classic case of the government over-reacting to a perceived problem”.

He said: “They [the proposals] are shocking in their breadth and range and would destroy the independent sector.

“They mistakenly advance the principle that political correctness equals British values. Accordingly, they could be used to punish any school in the independent sector that has a religious ethos, a set of traditional beliefs or who don’t over-promote every minority group’s worldview.

In response, a DfE spokesperson said: “The Independent School Standards are designed to ensure every school prepares children for life in modern Britain.

“We make no apology for demanding high standards and the promotion of tolerance and respect of all faiths and cultures.

“It is simply untrue to say that the proposed changes - which received 1,400 responses in the last six weeks - would prevent teachers using gender-specific terms or require schools to downgrade Christian festivals.

“We have received a letter from the Christian Institute’s legal representatives and are considering our response.”

When the new measures to promote British values were announced by Michael Gove, critics warned that it was a “knee jerk reaction” to the Trojan Horse incident.