A religious charity is threatening the Government with a judicial review over its plans for independent schools being introduced in the wake of the Trojan Horse plot.
The Christian Institute has branded the proposals "unlawful" and claims they will have serious and perverse consequences, such as requiring teachers to remove traditional and gender-specific terms like husband, wife, mother and father from the curriculum.
There are also concerns Christian schools will be forced to downgrade religious festivals such as Christmas so as not to offend atheists and those of other faiths.
As a result, the group has engaged lawyers and is threatening the Department for Education with a judicial review on the basis 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% 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 which has a religious ethos, a set of traditional beliefs, or who don't over promote every minority group's world view.
"Under the plans, private schools, academies and free schools would have much less control over their ethos than ordinary state schools."
The Independent School Standards consultation was begun in late 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.
Following the scandal, Education Secretary Nicky Morgan proposed that independent schools must "actively promote" British values.
Reacting to the institute's claims, a Department for Education spokeswoman 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."
Ghaffar Hussain, managing director of the Quilliam Foundation, told the BBC Radio 4 Today programme: "I really don't understand (Mr Hart's) concerns at all to be honest.
"I looked at the section that is put under discussion today and it says schools must actively promote specified principles including furthering tolerance and harmony between different cultural traditions and encouraging respect for democracy.
"British values are sufficiently vague and sufficiently open and sufficiently focused on things that most of us can agree on like the rule of law, democracy, respecting people from different backgrounds and cultures..."
Told that the vague definitions could raise a real problem if people have the ability to challenge them legally, Mr Hussain said: "I think they're vague but I think we know when individuals are encouraging exclusivist, isolationist mindsets or encouraging hatred toward certain groups in society that they're going against these values."
He added: "The key point here is we should not allow people to use religion as an excuse to encourage antipathy towards mainstream society or the values we as a mainstream society should be encouraging."
Mr Hart told the same programme he did not think he would disagree with Mr Hussain on that point, but added: "I think the problem is the way these things can be used and it can be completely over the top.
"Promoting transgender rights is not going to combat Muslim extremism. But... it's going to create its own form of extremism which in some cases is going to undermine the ethos of the schools.
"The Government talks about taking pupils round places of worship of different faiths. Why should a Jewish orthodox school be required to take pupils round a church or a mosque? That's up to them, isn't it? Why should the Government use the law to bounce schools into doing that - that undermines their ethos."
Mr Hart said he had no problem if teaching about other faiths to took place, but he added: "Why should you make schools with religious ethos comply in that way?
"The danger is we are taking specific things that arose in Birmingham and applying a blanket solution of political correctness which is going to be very damaging to British education."