In politics
Stuart was an unsuccessful Liberal candidate for the Cambridge University parliamentary seat in an 1882 by-election; in the 1884 by-election he was elected for Hackney.
From the 1885 election, Stuart sat for the Hoxton division of Shoreditch. He became known for his contribution to London politics, as the leading figure in formulating policies for the Liberal "London programme". He was one of the radical Liberals making up the management committee of the Liberal Publication Office, with James Bryce, Percy Bunting and Wemyss Reid. On 14 November 1888, in a House of Commons supply debate, Stuart made a detailed attack on the financial management of the Metropolitan Police. Charles Stuart-Wortley replied the next day for the Home Office. Stuart pressed his points on 3 December in the Daily News. A detailed rebuttal, including the comment that 1887 was an anomalous year given the Golden Jubilee of Queen Victoria, was produced in a memorandum by the Receiver for the Metropolitan Police District, Richard Pennefather.
In 1890, Sidney Webb wrote to Ramsay Macdonald, asking if anything could be done about the opposition shown by Thomas Lough to the "London movement" in general, and Stuart in particular. By 1891, however, Webb found Stuart's resistance to working-class Liberals troublesome, and stole a march with his own London programme. While Lord Rosebery was Premier, Stuart was keen to reform the University of London, but there were opponents including William Job Collins.
Stuart was an Alderman of the London County Council (LCC) from 1889 to 1898. He was an LLC councillor for Haggerston from 1901 to 1901. The Progressive Party on the LCC made him its leader around 1890; he stood down after the 1892 London County Council election.
In the 1900 general election, Stuart lost his seat in Parliament. He was returned for Sunderland from 1906, then again was defeated in January 1910. He was appointed to the Privy Council in 1909.