Hanne Stinson, chief executive of the British Humanist Association, responded to ongoing Cabinet discussions by saying that, in the interests of fairness, members should be there on an agreed basis of merit, irrespective of religion, according to theological think-tank Ekklesia.
Ms Stinson said Monday: "The UK is the only Western democracy to give religious representatives the automatic right to sit in our legislature and this anachronism should be top of the list for reformers.
"Modern Britain is a society with a staggering diversity of religious and non-religious beliefs."
Now the BHA is calling for reforms to the House of Lords to include the removal of the bishops who sit in the Lords as of 'right'.
The last time reforms to the Lords were under consideration, ecumenical and inter-faith bodies were consulted about the possibility of having their own seats or sharing places currently held by the Church of England.
While Congregationalists, Quakers and others objected to 'religious representation' on principle, the Church of England resisted reducing its bishops or including lay members, even from Anglicans in Scotland, Wales and Ireland.
The House of Lords currently has 784 peers, consisting of Lords Spiritual (senior Church of England bishops) and Lords Temporal (lay peers). Law Lords (senior judges) also sit as Lords Temporal. Members of the chamber are unelected and were originally drawn from the nobility and allies of the monarchy in Britain.
Free Church Christians, among others, have long opposed the presence of Church of England bishops in the House of Lords, who were given seats because of the Church's Establishment under the Crown.
Ms Stinson said: "Continuing to privilege one denomination in this way is preposterous and it would be just as unacceptable to extend the privilege to all religions. If the proposed reform includes appointments to the Lords these should all be on personal merit - there could be no objection to the occasional bishop or other religious leader being appointed on that basis."
Opponents to the Church of England bishops in the Lords remain skeptical, however, that the Government will propose any change, Ekklesia reports.
Ms Stinson commented: "The fact that the Government faced up to religious pressure recently over gay adoption has given some people reason to hope that they will not be as intimidated by [such] lobbying in the future, but the U-turn on faith school admissions last year and the recent [concessions] over issues such as religion or belief discrimination are not reassuring."