Schreiner was elected member for Malmesbury in 1898 and later that year became prime minister himself, heading a cabinet that included John X. Merriman and Jacobus Wilhelmus Sauer. As prime minister Schreiner favoured negotiation rather than hostilities, to the chagrin of the governor and high commissioner, Alfred Milner, who was actively fomenting war. Schreiner was forced to resign from the premiership and from Parliament in June 1900.
He failed to win a seat in 1904, but returned in 1908 as the member for Queenstown. He now adopted a liberal Bantu policy, influenced by a visit he had made in 1899 to the Transkei and the African leader John Tengo Jabavu. Schreiner advocated integration and equal rights for all "civilised" men. His dedication to this ideal was proved by his resignation from the National Convention in order to represent Dinuzulu, who was due to stand trial before a special court set up by the Government of Natal for his alleged treasonous participation in the rebellion of 1906.
Schreiner felt that the Union Government and Parliament proposed for South Africa would not uphold the liberal Bantu policy of the Cape Colony, so he went to London to oppose the passage of the South Africa Act through the British Parliament in 1909. He brought together a multiracial delegation of nine prominent Cape politicians to call for the Cape franchise which allowed all men of property to vote, irrespective of race, to be implemented in the whole of South Africa.[3] Schreiner led the group to London, but the delegation was unsuccessful in its appeal, despite receiving considerable support from the infant Labour Party and other liberal British organisations.[4] It was from this delegation that the African National Congress was formed in 1912.[5]
Schreiner was married in 1884 to Frances Hester Reitz, a sister of President F. W. Reitz. They had four children, including Oliver Schreiner, who became a judge.
^Report of Commission of Inquiry regarding Cape Coloured Population of the Union, U.G. 54 – 1937, Government Printer, Pretoria, 1937, p. 213, para 1037