Franklin was born in London in 1862, the son of Ellis Abraham Franklin, a banker and his wife Adelaide who was a sister of Samuel Montagu, 1st Baron Swaythling. In this way, Franklin was born into a Liberal family which also included Venetia Stanley, famous correspondent of H H Asquith and future Liberal Party leader, Herbert Samuel. In 1888 Franklin married Laura Agnes Ladenburg and they had one son and three daughters.
Franklin studied for the law and was called to the Bar at the Inner Temple in 1894, although he never practised. In 1892 he had become a partner in the firm of Keyser & Co. of Throgmorton Street in the City of London, foreign bankers and was a senior partner after 1929. During the First World War, he was appointed as Local Government Board representative at Folkestone with the task of dealing with the large numbers of refugees from 'gallant little Belgium' when the voluntary War Refugee Committee could no longer cope with the weight of numbers. For this work he was awarded the OBE. He was later posted to France to report on the finances of British military hospitals. Franklin also served as a Justice of the Peace.
Franklin undertook social work in London and was described as an 'ardent Radical.' From 1908, he was Chairman of North Paddington Liberal Association. He served as honorary treasurer of the London Radical Candidates' Association, taking a particular interest housing and traffic. In 1912 he and his wife Laura founded the Jewish League for Woman Suffrage which campaigned for national women's suffrage and for equal rights for women within the Jewish Faith. They were assisted by the extended Jewish family including Henrietta Franklin and her sister Lily Montagu.
Franklin first stood for Parliament at the December 1910 general election as Liberal candidate in Paddington North. He did not win the seat but he reduced the majority of the sitting Unionist Member of Parliament, Arthur Strauss from 893 to 598 votes. He fought the seat again at the 1918 general election but this time, as a supporter of the Independent Asquithian Liberals he was not favoured with the Coalition coupon and lost his deposit. At this election the former Tory MP, Arthur Strauss, had switched parties and was standing as an Independent Labour candidate. He too lost his deposit.
Franklin achieved the only Parliamentary win of his career at the 1923 general election. Standing in Central Hackney in a three-cornered contest, he obtained a majority over the Conservatives of 1,317 votes. However he was unable to hold the seat at the 1924 general election, falling to bottom place as the Tories regained the constituency and Labour jumped into second place. Franklin tried to win the seat back at the 1929 general election but again came third in a tight three-way contest, although this time it was the Labour Party which won the seat. Franklin's final attempt to regain Hackney Central came in the 1931 general election. He again came third, although this time by a wider margin, as the Conservatives took the seat back from Labour as the representatives of the National Government. Franklin remained an active supporter of the Liberal Party, playing a prominent role in the activities of the Hackney Central Association, right up until the outbreak of war in 1939.
Much of the social work which Franklin undertook was based in the Jewish community in London and he also held positions in respect of various synagogues. He was a vice-president of the Jewish Workingmen's Club and of the South Hackney Jewish Social and Literary Society.
Franklin was a strong supporter of the reform of proportional representation (PR) and invented a system known as Percentage PR. In 1922 he published the book Percentage Proportional Representation.
- Who was Who, OUP 2007
- Arthur Ellis Franklin, Records of the Franklin Family and collaterals; Taylor & Francis, 1915 p88
- The Times, 1 December 1932 p14
- The Times, 7 June 1894 p6
- The Times, 13 December 1944 p6
- The Times, 1 January 1892 p9
- The Times House of Commons 1931; Politico's Publishing 2003, p21
- Bernard Wasserstein, Herbert Samuel: A Political Life; Oxford University Press, 1992 p170
- The Women's who's who; Shaw Publishing Co., 1934 p176
- The Times, 26 July 1910 p12
- "Jewish League for Woman Suffrage | Jewish Women's Archive". jwa.org. Retrieved 22 November 2017.
- The Times House of Commons 1911; Politico's Publishing 2004 p27
- The Times House of Commons 1918; Politico's Publishing 2004 p21
- F W S Craig, British Parliamentary Election Results, 1918–1949; Political Reference Publications, Glasgow, 1949 p45
- F W S Craig, British Parliamentary Election Results, 1918–1949; Political Reference Publications, Glasgow, 1949 p20
- The Liberal Magazine – Volume 47 (1939)
- The Times, 3 June 1932 p19