A progressive education policy would seek to break down barriers between people of different faiths and beliefs, not erect them, writes NSS campaigns director Stephen Evans.

The schools adjudicator recently ruled against a new policy across all Catholic schools under which priests certify on a pupil-by-pupil basis whether a family is sufficiently pious for the pupil to merit a place at the local Catholic school.

So incensed is the Catholic church that it is considering taking the Government's schools admissions watchdog to court to protect the rights of priests to decide who can, or cannot, attend the local Catholic controlled school.

Under the policy parents wishing to apply for a school place are forced to obtain a Certificate of Catholic Practice (CCP), signed by a priest, to prove that their child is from a practising Catholic family.

This arbitrary approach clearly falls foul of the Admissions Code which requires admissions arrangements to be "fair, clear and objective". As one of the objectors pointed out, the CCP could lead to different priests applying different measures of practice.

That said, other mechanisms of proving your religious credentials are no less problematic. It's equally unfair to demand that parents regularly attend church in order for their children to attend the local school. This has resulted in many middle-class parents pretending to be religious in order to manipulate the system and get a place at their school.

One oversubscribed Church of England school in Lancashire is now considering insisting that parents attend worship for a minimum of two years in order secure a place. I'm sure this helps prop up church attendance figures, but where does this leave Justin Welby's claim that church schools must be "places of welcome for all, not cosy clubs for Anglicans"?

The relationship between religious adherence and school admissions in a liberal, secular democracy like Britain is an outrage that needs to end. Yet the Government's regressive plans to open a new wave of fully religiously selective schools means we can look forward to a lot more religious discrimination in years to come.

Department for Education guidance on 'promoting fundamental British values' calls it "unacceptable" for schools to "promote discrimination against people or groups on the basis of their belief, opinion or background".

I quite agree. But by dropping the 50% faith-based admissions cap, this is exactly the sort of discrimination that the Government is promoting. Perhaps Ofsted should consider putting the Government under special measures until it adequately promotes its own fundamental British values?

At the same time, the dropping of the 50% faith-based admissions cap will pave the way for yet more mono-religious and often mono-ethnic minority faith schools, which we all know will be disaster for social cohesion.

If our multi-racial, multi-cultural, increasingly secularised yet religiously diverse society is to succeed, pupils from an early age are going to need to learn to live respectfully and harmoniously alongside one another. You don't achieve that by fetishising faith and segregating children based on their religious background.

The collaboration between religion and state goes back a long way in Britain. What seemed reasonable and sensible in the 19th century today leads to division and discrimination.

A progressive education policy would seek to break down barriers between people of different faiths and beliefs, not erect them. Theresa May's plan to open up a new wave of discriminatory religious schools embodies retrograde thinking and sustains religious privilege.

The National Secular Society's message to Theresa May is clear. Don't extend religious discrimination and segregation in schools – end it.