The Lords Spiritual normally do not vote on matters of law or State in the House of Lords, but they have done so in special cases, such as during the passage of the Parliament Act 1911.
The occupants of the five "great sees" — Canterbury, York, London, Durham and Winchester — are always spiritual peers and Lords of Parliament. The Bishop of Sodor and Man and the Bishop of Gibraltar in Europe may not sit in the House of Lords regardless of seniority as their dioceses lie outside Great Britain. The former, though, sits on the Isle of Man's Legislative Council ex officio. Of the remaining 37 bishops, the 21 most senior sit in the House of Lords.
Theoretically, the power to elect Archbishops and Bishops is vested in the diocesan Cathedral's College of Canons. Practically, however, the choice of the Bishop or Archbishop is made prior to the election. The Prime Minister chooses from amongst a set of nominees proposed by the Crown Nominations Commission; the Sovereign then instructs the College of Canons to elect the nominated individual as a Bishop or Archbishop. See appointment of Church of England bishops.
Seniority is determined by total length of service as an English diocesan bishop (that is to say, it is not lost by translation to another see).
Even during the early years of the Peerage, the position of bishops was unclear. During the reign of King Richard II, the Archbishop of Canterbury declared, "of right and by the custom of the realm of England it belongeth to the Archbishop of Canterbury for the time being as well as others his suffragans, brethren and fellow Bishops, Abbots and Priors and other prelates whatsoever, — to be present in person in all the King's Parliaments whatsoever as Peers of the Realm." The claim was neither agreed nor disagreed to, however, by Parliament.
The Lords Spiritual at first declared themselves entirely outside the jurisdiction of secular authorities; the question of trial in the House of Lords did not arise. When papal authority was great, the King could do little but admit a lack of jurisdiction over the prelates. Later, however, when the power of the Pope in England was reduced, the Lords Spiritual came under the authority of the secular courts. The jurisdiction of the common courts was clearly established by the time of Henry VIII, who declared himself head of the Church of England in place of the Pope, ending the political power of the Roman Catholic Church in England.
Despite their failure to be tried as temporal peers in the House of Lords, it remained unclear whether the Lords Spiritual were indeed peers. In 1688, the issue arose during the trial of the Seven Bishops—William Sancroft, Archbishop of Canterbury; Sir Jonathan Trelawny, Baronet, Bishop of Winchester; Thomas Ken, Bishop of Bath and Wells; John Lake, Bishop of Chester; William Lloyd, Bishop of Worcester; Francis Turner, Bishop of Ely and Thomas White, Bishop of Peterborough—by a common jury. The charge was that a petition sent by the Bishops constituted seditious libel; the Bishops argued that they had the right to petition the Sovereign at any time, while the prosecution charged that such a right was only permissible when Parliament was in session (which, at the time of the delivery of the petition, it was not). If the Bishops were only Lords of Parliament, and not peers, their right to petition would be vitiated while Parliament was dissolved. Peers, however, were and still are counsellors of the Sovereign whether Parliament is in session or not; therefore, if the Bishops were indeed peers, they would be free to send petitions. Since there was no doubt that the petition was actually sent, while the Court still ruled the Bishops not guilty, it appears that it was taken for granted that the Bishops were counsellors of the Crown.
Nevertheless, the Standing Orders of the House of Lords provide, "Bishops to whom a writ of summons has been issued are not Peers but are Lords of Parliament."
In addition to the 21 older dioceses (including four in Wales), Henry created six new ones of which five survived (see Historical development of Church of England dioceses); and then for nearly three centuries no new sees were created. The number of lords spiritual remained at 26 all this while.
When in the 19th century the dioceses of the church began gradually to come under review again, an increase in the bench of bishops was not considered politically expedient, and so steps were undertaken to prevent it. In 1836, the first new bishopric was founded, that of Ripon; but it was balanced out by the merger of the Bishoprics of Bristol and Gloucester. (They were later divided again.) The creation of the Bishopric of Manchester was also planned but delayed until St Asaph and Bangor could be merged. They never were; but in 1844, the Bishopric of Manchester Act went ahead anyway with an alternative means to maintain the 26-bishop limit in the House of Lords: the seniority-based proviso which has been maintained to this day.
The 26 Lords Spiritual currently represent just under four percent of the total membership of the House of Lords.
The presence of religious leaders in the British legislature is strongly opposed by secularist organisations such as the British Humanist Association and the National Secular Society who have consistently campaigned for their removal.