Northcote for his substantial success in persistently urging tho need of revival of parliamentary control over the estimates and government expenditure. Montagu, who published in 1852 a treatise on ship-building, suggesting a new method of laying down vessels, on 19 May 1862 pleaded with practical effect for export advice in ship-building, for plated ships of war in the public of wooden vessels, and for the establishment of a naval school of architecture and engineering on the model of tho Woolwich military academy. In foreign affairs Montagu was no less active and sensible. He opposed Roebuck's resolution (30 June 1863) for recognition of the confederation of the southern states of America, and he spoke strongly in favour of non-intervention between Denmark and the German powers (5 July 1864). In later years he gave much attention to the Eastern question. On the reform question Montagu showed individuality. He feared the policy of multiplying the ignorant voter, and advocated plurality voters, with additional franchises to property and the professions. On social questions Montagu's attitude was more liberal. So early as 1860 he supported a measure for a council of conciliation in labour disputes ; and in 1875, in a debate on the employers and workmen bill, he declared trades unions to be 'not only a natural right but a preservative of order.' On Montagu's motion (April 1864) a select committee on which he sat inquired into the disposal of sewage in large towns ; and subsequent legislation on the subject owed much to his labours. On 19 March 1867 Montagu was made, on the reconstruction of Lord Derby's third ministry, vice-president of the committee of council on education, and was appointed first charity commissioner, being sworn of the privy council. He held office till Disraeli's resignation in December 1868. As education minister Montagu sought vigorously to enforce the conscience clause in all schools which received grants from public funds, and advocated the extension of technical education. He carried a bill assimilating the vaccination procedure of England to that of Scotland and Ireland, and took effective measures to deal with a serious cattle plague which had spread from the Continent to England. While in opposition Montagu, as an adherent of the old system, actively criticised the education bill of 1870 and its successors. His views on the Irish question came to differ from those of his party, and during the parliament of 1874-80 he sat for Westmeath as a oonservative home ruler. He left the home rule organisation in 1877, but remained out of harmony with Disraeli's government. To its vacillation he mainly assigned the Bulgarian agitation, and be condemned the Afghan policy of Lords Salisbury and Lytton.
On his retirement from parliament in 1880 Montagu devoted himself to religious controversy. In 1864 he had defended church establishments and upheld Anglicanian in 'The Four Experiments in Church and State and the Conflicts of Churches' ; but in 1870 he became a Roman catholic, and in 1874, in 'Expostulation in extremis,' attacked Gladstone's 'Political Expostulation on the Vatican Decrees.' In the same year, too, he published, as the first volume of St. Joseph's theological library (a Jesuit series), a treatise 'On Some Popular Error in Politics and Religion.' an adaptation of P. Secondo Franco s 'Risposte popolari alle obiezioni più diffuse contro la religione.' In 1882 Montagu rejoined the English church on ethical and political rather than on theological grounds (see his Reasons for leaving the Church of Rome, 1886). Thereupon he pursued a vigorous campaign against Romanist doctrine and practice, professing to expose a conspiracy in which the leaders of both political parties were involved, to bring England under the dominion of the papacy (cf. his Recent Events, and a Clue to their Solution, 1888, 3rd edit. 1888; Scylla or Charybdis, which? Gladstone or Salisbury? 1887). 'The Sower and the Virgin' (1887) was an exhaustive confutation of the doctrines of the immaculate conception and papal infallibility. 'The Lambeth Judgment, or the Marks of Sacerdotalism' (1801) minutely analysed Bishop King's case.
Montagu, whose independence and sincerity unfitted him for success in political life, was widely read and spoke with fluency. He died at 91 (Queen's Gate, Kensington, on 6 May 1902, and was buried at Kensal Green. He married (1) on 12 Feb. 1860 Mary (d. 1857), only child and heiress of John Gkoniie, of Cromore, co. Antrim, by whom he had two sons and two daughters; (2) on 18 Oct. 1882 Catherine (d. 1897), daughter of William Wade; by her he had three sons and two daughters.
In addition to the works cited and other tracts, theological and political, Montana published : 1. 'A Few Words on Garibaldi,' three edits. 1861. 2. 'A Mirror in America,' 1861 (a polemic against party spirit). 3. 'Foreign Policy: England and the