Indies,’ which was formed under his auspices, a bequest of the Hon. Robert Boyle, made in 1691 for missionary work in America, but, owing to the altered state of affairs in America, no longer available for that purpose. He was an early patron of the Church Missionary Society; and it was at his suggestion that Dr. Claudius Buchanan [q. v.] wrote those works which mainly led to the foundation of the Indian episcopate. He joined the British and Foreign Bible Society, and suggested the name of John Shore, lord Teignmouth [q. v.], as its first president, while he himself accepted the post of vice-president. He had at all times the courage of his opinions, took on all subjects an independent line, and identified himself with no one party in the church. Though he was sometimes called ‘a Methodist,’ he was strict in enforcing the discipline, as well as the doctrine, of the church; and he incurred considerable odium by excluding from the parish churches of his diocese a clergyman (Dr. Draper) who had accepted the presidency of a college in Lady Huntingdon's connexion, and had preached in a chapel belonging to that lady. In 1779 he was in favour of the relief of the Roman catholics from penal laws, but he strongly opposed ‘Catholic Emancipation,’ especially the bill of 1805, on the ground that it is one thing to grant perfect toleration, quite another to confer political power. As diocesan for the church abroad, he maintained his right of veto upon the appointment of chaplains by the East India Company.
One of Porteus's chief aims was to secure the due observance of religious holidays. A letter which he addressed to his parishioners at Lambeth in 1776, on the neglect of Good Friday, led to a stricter observance of that day throughout London (see Brydges, Restituta, iv. 417). The letter was subsequently published as a tract by the Society for Promoting Christian Knowledge. In 1780 he had taken a leading part in putting down two Sunday practices in London—viz. the Sunday debating societies, which were, in fact, assemblies for ventilating and propagating sceptical views; and the Sunday promenades, which had degenerated into meetings for assignations. When bishop of London he waged war against the custom of having Sunday concerts at private houses by professional performers, writing a letter to three ladies of rank who had helped to introduce them; and not long before his death he sought an interview with the prince regent (afterwards George IV), whom he persuaded to alter the day of meeting of a Sunday club which the prince had patronised in London. Pamphleteers bitterly attacked him, but he was indifferent to their onslaughts (Life, p. 272). At the same time he vigorously resisted the spread of French revolution principles, which he regarded with alarm. Paine's ‘Age of Reason’ he described as ‘rendering irreligion easy to the meanest capacity;’ and he warmly encouraged by way of antidote the dissemination of Hannah More's popular tracts. To counteract the spread of infidelity and the ‘growing relaxation of public manners,’ he delivered in St. James's, Piccadilly, Friday-evening lectures during four successive Lents, beginning in 1798. They were attended by crowds.
Porteus had ample means, and made a liberal use of them. He was generous to the poorer clergy, and attempted to raise the status and the stipends of assistant curates. In 1807 he built and endowed a chapel of ease, with a residence for the minister, in the parish of Sundridge, to which he loved to retire of a summer. On 28 May of the same year he gave 1,200l. to his old college (Christ's) for the endowment of three medals—one for a Latin dissertation on some evidences of Christianity; another for an English essay on some precept of the Gospel; and the third for the best reader of the lessons in the college chapel. He died at Fulham on 8 May 1808, and, according to his own desire, was buried at Sundridge. On 13 May 1765 he married Margaret, eldest daughter of Bryan Hodgson, landlord of the George Inn, St. Martin's, Stamford, afterwards of Ashbourne in Derbyshire; she survived him. There is a good portrait of the bishop, drawn by H. Edridge and engraved by C. Picart, of which both full-length and half-length copies were taken. The half-length copy forms the frontispiece of his ‘Life.’ Another portrait, which is anonymous, belongs to the bishop of London.
Porteus was a pleasing and effective preacher and writer. Besides several charges, volumes of collected sermons, and hortatory letters already noticed, he published: 1. ‘A Review of the Life and Character of Dr. Thomas Secker, Archbishop of Canterbury,’ 1770, which went through twelve editions. 2. ‘The Beneficial Effects of Christianity on the Temporal Concerns of Mankind proved from History and Facts,’ about 1804; 9th edit. 1836. 3. ‘A Summary of the Principal Evidences for the Truth and Divine Origin of the Christian Revelation,’ 1800; 15th edit. 1835. Many of his works were collected in ‘Tracts upon Various Subjects’ (1796). His ‘Complete [Prose] Works’ were published in 6 vols. 8vo; a new edition was published in 1816.