Pivotal figure of British left and great parliamentarian of post-war era

Tony Benn, who has died aged 88, was a pivotal figure in British left-wing politics in the second half of the 20th century. A national institution, instantly recognisable from his distinctive voice, intense self-belief and fondness for a mug of tea and a pipe, he was held in sufficient regard that even his critics usually found some aspect of his life or career to praise.

It had not always been so: Harold Wilson maintained that Benn immatured with age; and the right-wing press came to call him the most dangerous man in Britain.

Stagflation and industrial militancy destroyed Edward Heath's Tory government in 1974. The battle between Benn's ideas and those of the new right for addressing the crisis of British capitalism and democracy shattered the centre of British politics. Public opinion was more receptive to the views of Margaret Thatcher.

In the process she inflicted an epochal defeat on the British left. Benn was not responsible for Thatcherism, but some have argued that the only thing that would have damaged the left more than Benn's failed attempt to capture the Labour Party would have been his success.

After narrowly losing the contest for the deputy leadership in 1981, he withdrew from practical politics and launched one of the greatest rhetorical projects of the modern era.

From an early age he had kept a diary, and from 1964 he updated it nightly. Later he started recording every speech and meeting. He published volume after volume of revealing and insightful diaries, polemical essays and the videos of his speeches.

His grandfathers were Liberal MPs, as initially was his father, William Wedgwood Benn. In 1923 the latter joined Labour and served in Ramsay MacDonald’s and Clement Attlee’s governments. In 1942 he reluctantly gave up his Commons seat to bolster the war-time coalition’s Labour contingent in the Lords, accepting a hereditary peerage as Viscount Stansgate.

William and his wife Margaret created a happy, industrious and religious London household, with three sons – Tony was the second . From Westminster school he went to New College, Oxford, to study philosophy, politics and economics.

After second World War service in the RAF (1943-'45) he returned to Oxford and graduated in 1948, spent time in the US, and worked as a BBC radio producer (1949-'50). He was known formally as Anthony Wedgwood Benn, or Wedgie by friends and family, until in 1972 he settled on plain Tony Benn.

In 1949 he married a wealthy American, Caroline Middleton DeCamp, a socialist, educationist and biographer, and they too built a happy domestic life in Notting Hill, west London.

Their daughter Melissa and three sons, Stephen, Hilary and Joshua, were all active politically, with Hilary becoming a Labour cabinet minister.

He entered parliament through the Bristol South East byelection of November 1950, a conventional centre-right backbencher. His elder brother Michael had been killed in a flying accident while on active service in 1942, leaving Tony the eldest sibling. He would thus one day be Lord Stansgate and have to give up his seat.

Throughout the 1950s, he was generally known as a broadcasting expert, an advocate for the modernisation of Labour’s electoral strategy and as a campaigner on colonial issues.

Initially a follower of Hugh Gaitskell, the party's leader from 1955, Benn switched to Wilson when Gaitskell proposed revising clause four of the party constitution in 1959, a clause that committed to nationalise the means of production.

In 1960 Benn’s father died, disqualifying him from remaining in the Commons. After a three-year struggle he gained the support of the Conservative government for the Peerage Bill, allowing him renounce his title. His Conservative opponent in Bristol South East, Malcolm St Clair, stood down, and Benn won the resulting byelection, returning to the Commons.

When Labour won in 1964, Benn was appointed postmaster general. He was generally effective and, in the 1960s, well-liked by most of his civil servants.

According to cabinet colleague Tony Crosland, Benn welcomed Labour's defeat in 1970. He became heavily involved with the Alternative Economic Strategy developed with Stuart Holland and Judith Hart, which he articulated in Arguments for Socialism (1979). If the problems of democracy could be cured by more democracy, then planning and nationalisation would cure the problems of the British economy, he argued.

Following the rapid increase in oil prices and the chaos of the Heath government’s confrontation with the miners, there appeared to be no future in the status quo. Democracy and capitalism seemed equally impotent in the face of a global crisis of economic, social and political confidence. Benn’s radical critique of the 1964-’70 Wilson government now chimed well with the militancy of the shop stewards’ movement.

But Benn was not surefooted. He opposed joining the EEC and championed a referendum on Britain’s membership, but saw the Yes campaign win. He was a leading figure opposing the use of wage restraint on trade unions but saw the policy reversed. Having been given a key economic ministry, he was demoted to energy.

From then on he was a “dissenting minister” in the government, a leader of those across the Labour movement frustrated by the government’s lack of radicalism. When Labour lost the 1979 general election, Benn was well placed to assume the leadership of the left, and began to propose constitutional changes to give greater representation to activists’ views.

Despite Michael Foot's passionate appeal for unity, Benn stood against Denis Healey in the September 1981 election for the deputy leadership. Healey won, under the reformed system that Benn had championed, by less than 0.5 per cent.

Labour began the long, hard climb back to power. The left of the party split, with the Tribune group backing Foot and later Neil Kinnock, and Benn setting up his own Campaign group in 1982. When Kinnock took over after the election, the high tide of Bennism had been reached.

Losing his seat in boundary changes, he returned at a byelection in Chesterfield in Derbyshire in March 1984. When he stood for the leadership in 1988, he was heavily defeated. In 2001 he retired from the Commons “to devote more time to politics”.

The major elements of the Bennite critique of British capitalism were that Britain needed a siege economy to protect domestic industry; nationalisation or selective share ownership of the top 25 to 100 companies and joint-stock banks; wide ranging constitutional reform; withdrawal from the Common Market, Nato and Northern Ireland; and unilateral nuclear disarmament.

His world-view presented a well worked-out analysis, according to which the IMF, World Bank and multinational corporations ran the global economy. The European Commission and the establishment governed Britain. The US was an imperial power that had pursued a policy of world domination since the second World War.

From the mid-1970s onwards, Benn ceased to have anything new to say as a political thinker. The rest of his life was spent trying to make current events fit his outlook and condemning those who changed their minds and positions. As Benn’s mind closed to alternative positions, so the part of the British left that he led became deeply conservative.

The roots of Benn’s socialism were stubbornly non-Marxist. He did not arrive at his worldview through historical materialism as much as through the Bible. He was therefore always a slightly awkward leader of the economic determinists of the left.

The urge to question and challenge authority made him one of the great parliamentarians of the post-war period. With Foot, Enoch Powell and a handful of others, he had the ability to command the house’s attention, especially when he spoke of matters relating to its own rights and privileges.

In 1987 the first volume of his diaries appeared, covering the period 1963-'67. Subsequent volumes then appeared almost annually, covering all of his career. The final one, A Blaze of Autumn Sunshine (2013), in which he movingly described Caroline's death from cancer, was serialised in the Daily Mail .

Caroline died in 2000 and he is survived by their children.