Lehane was born in
Belfast, Northern Ireland on 7 May 1912, the only surviving child of Denis Lehane, an excise officer originally from
County Cork, and his wife Mary (née Connolly), a native of the
Falls Road, Belfast. He grew up in an Irish-speaking household. He qualified as a solicitor. He married Marie O'Neill in 1937, and they had a son and two daughters. As a solicitor, he took to defending members of the
Irish Republican Army (IRA) in the Irish Courts. He was active in other
Republican and Nationalist circles: he was a member of the Moibhí Branch of
Conradh na Gaeilge, and by the 1930s seems to have become active in the IRA itself. In 1931 he was involved in
Saor Éire, an attempt by the Irish left-wing to create a communist political party that would have been linked to the IRA. Lehan was arrested on 23 March 1935 during a series of raids on the homes of prominent Irish Republicans and members of the
Republican Congress (44 men were taken into custody). He was sentenced to 18 months imprisonment by the Military Tribunal for sedition, membership in an unlawful organization (the IRA) and refusing to give an account of his movements. He retired from the IRA in April 1938 with
Seán MacBride as they were not prepared to support the planned
bombing campaign in the United Kingdom during World War II. In 1940 he was a member of
Córas na Poblachta, another attempt to build a Republican political party backed by the IRA. Interned again in 1940 under the
Offences against the State Acts 1939–1998 Lehane was made a commanding officer of the IRA prisoners in
Arbour Hill Prison. While interned Lehane and five other Irish Republican prisoners went on a 26-day hunger strike, protesting being imprisoned without trial. ==Clann na Poblachta TD==