Callaghan was an old-style socialist, lacking any higher education, and served as MP for Cardiff North. He was Chancellor of the Exchequer at the time of the devaluation of the pound in 1967 and resigned this office in the aftermath. Having been appointed Home Secretary, his background in the trade union movement meant that he served as a focus for opposition to the employment laws proposed by his cabinet colleague Barbara Castle in 1969. In this struggle (called The Battle of Downing Street) he ultimately prevailed, and the proposals (set out in the White paper[?] In Place of Strife) were dropped.
Callaghan was the first prime minister to have held all three leading Cabinet positions - Chancellor of the Exchequer, Home Secretary and Secretary of State for Foreign and Commonwealth Affairs- prior to becoming prime minister. He was never expected to reach the latter position, having taken a back seat to the younger and more charismatic Harold Wilson for many years. However, when Wilson unexpectedly announced his retirement in 1976, Callaghan was the most experienced candidate to replace him. His time as prime minister was one of more open government, but the public was dissatisfied with his relaxed response to high inflation and the increasing industrial unrest (culminating in the Winter of Discontent) and replaced Labour with a Conservative government under Margaret Thatcher.
Callaghan resigned as leader of the party eighteen months later, on the occasion of the 1980 party conference. He remained an MP for some years before being elevated to the House of Lords as Baron Callaghan of Cardiff.
Callaghan's resignation as party leader ignited a power struggle between the left and right wings of the party which culminated in the defection of the Gang of Four to found the SDP. Many commentators hold the view that this struggle was inevitable and even blame Callaghan for not resigning earlier. Callaghan's admirers maintain that had he remained as party leader his position would have been respected by both sides and that by avoiding a split in the non conservative vote he could have restored the Labour Party to Government by the mid-1980s. This disagreement is illuminated by the fact the Callaghan's successor, Michael Foot, a compromise candidate from the left of the party, was unable to prevent Tony Benn from challenging his right wing deputy Denis Healey.