Bishops who represent the Church of England in the House of Lords are facing criticism, after failing to attend a debate on faith school admissions policies.
Peers were discussing a UN call for a ban on religion being used as a selection criteria in schools.
Many faith schools in the UK give preference to pupils who are linked to a church.
Addressing the issue, Liberal Democrat Baroness Burt of Solihull said: "Not a lot of people know this, but children from non-religious families may experience double discrimination when it comes to selection at schools. Approximately 40% of all faith schools and 60% of Catholic schools give priority to children of families of any religion against those of no religion."
Backing the UN resolution, she added: "Does the minister agree that all children, irrespective of faith or belief background, should have equal right to access schools funded by taxpayers' money?"
In response, speaking for the government, Lady Barran said: "We believe that all children have equal access. Only when a school is oversubscribed can the admissions authority introduce additional restrictions. Indeed, many faith schools do not restrict on the basis of faith."
Addressing the absence of bishops during the debate, Conservative peer Lord Cormack said: "It is a great pity that, of the 26 of them entitled to sit in the House, there is no bishop here to defend the wonderful contribution that the established church has made to education through the centuries.
"Should we not pay proper regard to that and, in doing so, accept that Christian parents should have some degree of priority if there are vacancies in a Church of England school?"
A Church of England spokesperson said: "The Bishop of Bristol was on duty but was not able to attend owing to an important meeting involving a cross-party group of MPs and peers.
"She regrets not being in the chamber for the question on schools, but is grateful for the contributions in support of the Church of England's schools made by Lords Baker, Carey and Cormack, and for the minister's words."