Socialism's first lady - Barbara Castle was exasperating, insecure and determined to the point of obsession. But, as a minister, her achievements were impressive. Jack Straw remembers Labour's most successful female politician

Red Queen: the authorised biography of

Barbara Castle

Anne Perkins <em>Macmillan, 499pp, £20</em

Barbara Castle "had the provocative confidence to argue . . . that if she was doing it, it must be socialism", writes Anne Perkins in her aptly titled book Red Queen. While this may be the authorised biography of an extraordinary woman, it is certainly never hagiographic. As her mother was dying, Barbara remarked "that she was endearing, much loved and totally exasperating". Like mother, like daughter.

I was Barbara's political adviser for two intensive years during her last period of office as social services secretary. I took over her Blackburn constituency in 1979, and saw a good deal of her between then and her death last year. Life for all of us who were close to her was extremely unpredictable: one minute you were her favourite son, the next you were relegated to outer darkness, and back again. Perkins does an excellent job with this most difficult subject, painting a sympathetic but far from uncritical portrait of Labour's most successful female politician. Castle might easily have preceded Margaret Thatcher as Britain's first female prime minister, had she not so prematurely pressed the self-destruct button with her disastrous handling of the white paper In Place of Strife - her 1969 attempt to reform industrial relations.

Although I knew Barbara pretty well, much in this biography was illuminating. Her bombastic, breathless style disguised far deeper insecurities than I had ever realised. These stemmed, perhaps, from her intellectually brilliant but distant father (who read Greek verse on the Bradford tram on his way to work as a tax inspector); he was overbearing and evidently never satisfied. In her finals at Oxford, she thought she had failed, but in fact she scraped a Third. Others might have brushed this off, but for Barbara, as Perkins shows, it led to a pervasive sense of intellectual inferiority - particularly in relation to the cabinet's Oxford mafia of Wilson, Healey, Jenkins, Crosland, Crossman and "Wedgie" (Benn) - for which she was constantly trying to compensate. She would never talk about her Oxford days, except to say they had "not been happy"; and she was only occasionally wistful about her inability to conceive. But this, and the premature death in 1942 of the one true love of her life, William Mellor (more than 20 years her senior and, in part, her father reincarnate), gave her a strong sense of loss. I guess it was Barbara's nature to be pretty self-regarding; but no doubt these disappointments reinforced the barriers she erected around herself, and made her one of the most self-absorbed people I have ever met.

"Battling Barbara" was how she liked to see herself. She was never happier than when she had a fight on her hands, and mostly she was victorious. She was, I think, a nightmare for colleagues who had to work with her (the very idea is almost an oxymoron); but it was a great privilege to work for her. She was strategic and focused; she understood that it was not just the grand design which mattered, but its detailed application; and she was determined to the point of obsession. She built a substantial following in her Blackburn constituency because of her clear commitment to the town.

Castle's achievements as a minister were impressive, including the establishment of what is now the Department for International Development, the breathalyser, other important transport reforms, equal pay for women, Serps pensions, and much else.

What makes Red Queen an important work, alongside its fluency, is Perkins's broad understanding of Labour's history and the party's propensity to resort to the kind of visceral internal fighting that led to the end of each of the three previous postwar Labour administrations and put us out of power for 35 of the past 57 years. Barbara had a commendably strong sense of injustice, but she was also a partisan with an abiding contempt for those on the right of the party (and sometimes for anyone - left or right - who disagreed with her). Like too many in the party at the time, she appeared to think that the electorate would not be too bothered if the party's leadership devoted almost all of its energies to kicking the guts out of each other: you could kiss and make up just before an election and it would all be fine. There is a revealing photograph of Gaitskell, Bevan and Barbara in a warm embrace just before the 1959 election. But the public is not daft. Labour went down to a thumping defeat that year, as it did on so many dismal occasions before and since - and always for the same reason.

Barbara fell, and never properly recovered, as a result of the humiliating failure of her greatest project - reforming the trade unions. Perkins is balanced and generous in her assessment. "History," she writes, "is a kinder judge", and goes on to quote Bernard Ingham (Barbara's press officer at the time) that Castle's proposals "genuinely represent[ed] the first attempt to come to terms with an abuse of power". Thirty years and the Thatcher revolution on, Barbara's ideas do indeed look both historic and relatively moderate. But timing and consent are all in politics, and tragically Barbara got both wrong. The timing - though to a large degree forced by mounting public antipathy to "wildcat" strikes - was too close to the election, and coincided with a tight prices and incomes policy. One, or the other, might have been possible, but never both at the same time.

Worse, however, was the problem of consent. First, the cabinet was bypassed to an astonishing extent. Naturally, I am aware of the contemporary debate about the changing role of the cabinet. Up to the end of the 1970s, the cabinet had a more formal role than during these past 25 years. Under changes initiated by Thatcher, much more business came to be dealt with in cabinet committees, ad hoc ministerial groups and prime ministerial bilaterals. But this has not been a one-way process. Select committees, freedom of information and the Human Rights Act have required much greater openness and transparency of decision-making.

Sometimes under Wilson, the most basic tenets of cabinet government were simply ignored. In Place of Strife was drafted by Wilson and Castle in such secrecy that the first the cabinet knew about it was when Roy Jenkins - who was in the know - had the plan leaked by his PPS Tom Bradley. There began open warfare, with the then home secretary, Jim Callaghan, leading the opposition. Barbara decided to brief the TUC and CBI "in confidence" before Christmas 1968, but the cabinet not before early January. Then it was leaked again. She battled on until mid-June 1969, but the saga ended with the infamous "Declaration of Downing Street", when her sole remaining cabinet ally - an already weakened Wilson - deserted her.

And the lessons for today? By the coruscating standards of the 1960s and 1970s, and the vitriol of the 1980s, Labour's arguments today - on Iraq, foundation hospitals, tuition fees - are remarkably civilised. But the warning signs are there. In the late 1960s, Wilson had a large majority (97). We have a bigger one still. Big majorities are obviously better than small ones. They provide something of a mandate for bold decisions and also a cushion for the ensuing controversy. But in addition, they can lull some parts of the governing party into a deceptive sense of security - a belief that evermore vocal internal opposition is a good thing. This is an even greater risk today, given the abject Tory opposition. As we approach 2 August, when Tony Blair's government will become the longest-serving Labour administration, we would do well to remember the pain of the past, so vividly described in Perkins's book.

Jack Straw is Foreign Secretary