Janner entered politics in 1920 when he stood unsuccessfully for election to
Cardiff City Council as a candidate of the
Comrades of the Great War. Three years later he had joined the
Liberal Party, but again failed to gain a seat on the council. In 1926 he was elected to the
Board of Deputies of British Jews, and subsequently became a member of the executive of the British
Zionist Federation. At the
1929 general election he was the Liberal candidate for
Cardiff Central, but failed to be elected. Later in the year he moved to
Hendon, north London, and took up employment as company secretary and solicitor for his father-in-law's business. In 1930,
Harry Gosling, the sitting Labour
MP for the
Whitechapel and St George's constituency in the
East End of London died. Janner was chosen to contest the resulting by-election. The area had a large Jewish population, and he campaigned in opposition to the government's policy on Palestine, but was narrowly defeated. Ten months later at the
1931 general election Janner again contested the Whitechapel seat for the Liberals, this time being returned to the House of Commons. At the
next general election in 1935 Janner stood as a Liberal and Anti-Fascist candidate, but was one of many Liberals to lose their seats, with the Labour Party regaining the seat. ==Labour politics==