Politics
During the years he was working at Hutchinson's in Widnes, Brunner was developing his political interests. He joined the Widnes chapter of the National Education League and became its secretary in 1872. This gave him the opportunity to come into contact with Liberals from Liverpool and other parts of the country. Soon after moving to Northwich Brunner became more practically involved with education locally, in particular with the British School in the town. He later served on its board of governors and also on the local sanitary authority. As a result of the Redistribution of Seats Act 1885 the parliamentary constituency of Northwich was created and Brunner offered himself as a candidate for the Liberal Party. In his speech for the position he expressed support for the disestablishment of the Church of England, for reform of property laws, for Irish Home Rule and for compensation for those whose properties had been damaged by the pumping of brine from the salt mines in the area. During the campaign he was heckled because he had a foreign-sounding name. He responded "My father was a Swiss, my mother was a Manx woman, I was born in Liverpool, my nurse was Welsh: is that Cheshire enough for you?" At the general election on 1 December 1885 Brunner beat William Henry Verdin, his Conservative rival, with a majority of 1,028.
The Liberal Party won more seats than any other party in the election, but insufficient to form a majority government, leaving the Irish Parliamentary Party holding the balance of power. It proved impossible to form a stable government, and so another general election was called in June 1886. In the meantime, the Liberal Party had split, and the Liberal Unionist Party had been formed. Brunner's opponent at the 1886 election was William Henry Verdin's brother, Robert, standing as a Liberal Unionist. The election was held on 13 July 1886, and Brunner was defeated by 458 votes. In November 1886, Brunner embarked on a world tour, accompanied by his wife and his son Stephen. His return to Northwich on 2 July 1887 was greeted with great celebration, as he was extremely popular in the town, regarded as a kind and sympathetic employer and a generous benefactor. Within three weeks of Brunner's return, Robert Verdin died and a by-election was called. Brunner's opponent was Lord Henry Grosvenor, who was standing as a Liberal Unionist. This time, at the by-election on 13 August, Brunner won with a majority of 1,129.
After the 1889 Armagh rail disaster, Brunner opposed moves to regulate safety on railways, saying during a debate on 2 August that safety should be left in the hands of "those who understand these matters best", i.e. the railway companies. But the government moved rapidly to have railway operations and safety supervised by the Board of Trade.
At the 1892 general election, Brunner's opponent was not a Liberal Unionist, but a Conservative, George Whiteley, who was a cotton manufacturer from Blackburn. Brunner was returned with an increased majority of 1,255. In the 1895 election he beat Thomas Ward, another Conservative, by 1,638 votes. The 1900 general election was held during the Boer War, to which Brunner was opposed. He retained his seat, but with a reduced majority of 699. In the 1906 general election, Brunner's opponent was the Conservative Colonel B. N. North who had fought in the Boer War. Brunner increased his majority to 1,792. He continued to be the Member of Parliament for Northwich until the general election in January 1910, when he decided not to stand again, partly because of his own health and also because of concern for his wife's health. Subsequently, he moved to Surrey, but continued to play a part in politics when he was elected to the Chertsey division of Surrey County Council.
As a Liberal MP he supported Irish Home Rule, trade unions, free trade and welfare reforms. Leading up to the First World War he argued that Britain should adopt a more sympathetic approach towards Germany, including naval disarmament. When war did break out, Brunner was resolute in the opinion that it should be fought and won. In addition to the production of alkali, his factories were making other chemicals for use as explosives. He also built a new factory to purify trinitrotoluene.