The Ecclesiastical Titles Act 1851 was an Act of the British Parliament (14 & 15 Vict. c. 60) passed in 1851 as an anti-Roman Catholic measure. It was ineffective and was repealed 20 years later by the Ecclesiastical Titles Act 1871. It was legislation demanded by prime minister John Russell in the wake of widespread popular "no popery" outbursts in 1850 when the Catholic Church set up a network of its own bishops in England. Anti-Catholic elements denounced the Papal move as "papal aggression." The new law was the last effort made to repress a Christian church, and was repealed in 1871. Catholic bishops officially followed the law but rank-and-file Catholics ignored it. The effect was to strengthen the Catholic Church in England, but also it felt persecuted and on the defensive.
When the church in England and Wales was established as an independent Church of England in the 16th century, it continued to use the same buildings and hierarchy as hitherto. Hence, the titles of Archbishop of Canterbury and Bishop of London (for example) continued in use, with the incumbents holding authority over the same areas, and the same held for the whole of the Church of England hierarchy. The position in Scotland would be more complex, due to internal disagreements about episcopalianism. In Ireland, the Catholic hierarchy continued to use the titles of the ancient sees.
In 1850, in response to the Catholic emancipation legislation, Pope Pius IX set up a Roman Catholic hierarchy of dioceses in England and Wales in Universalis Ecclesiae. This was met with widespread hostility, and many characterised it as an act of "papal aggression", although, because the Roman Catholic Relief Act 1829 (Statute 10 of George IV, chapter 10) had forbidden the use of the old titles except by the clergy of the established Protestant Church, the Catholic Church had refrained from using the ancient titles of the existing Anglican sees, and had created new titles for their bishoprics. Thus they did not name the relevant see that of Bristol, but that of Clifton; not Exeter, but Plymouth; not Canterbury, but Southwark. The selection of Westminster as the title of the principal see in London, however, was nevertheless seen by critics as presumptuous for Westminster had long been identified as a major centre of the English church.