Campbell was married to the Morning Star journalist Bobby Campbell, a folk musician who went on to work at The Scotsman in the 1970s. At the age of 23, while still married, she came out as a lesbian. Campbell is co-author with Judith Jones of a book Stolen Voices (withdrawn under the libel laws) and a play, All the Children Cried.

Campbell joined the Communist Party of Great Britain around the time it was turning itself from a bulwark of trade union officialdom, towards a more feminist and multi-culturalist programme. She joined a reform faction founded by University lecturer Bill Warren in 1970. and was one of the 'Gramscians' who 'took leading positions in the party' when she joined the National Women's Advisory Committee.

At that time, Campbell excused the party membership's identification with Stalinist oppression in Eastern Europe: " in the main it is a solidly working class part of the Party which is called Stalinist only by virtue of the fact that they thought the CIA was about to take over Czechoslovakia and it was therefore politically correct that the Russians moved in." However, Campbell did use the label 'Stalinist' as a negative, but what she meant by 'Stalinist' was those elements in the Communist Party who criticised the line put forward by its leadership. So she condemned the "Stalinists in the party who have actually realised a position which is a very comprehensive criticism of where the leadership is going".

In 1977 Campbell defended the Communist Party's revolutionary credentials: "There is no way it is legitimate to say that the party isn’t revolutionary... the defeats, the comings and goings doesn’t make it an organisation that sells out the masses." Thirteen years later, though, her hostility to radical protest was writ large in a report on the Poll Tax riots: "when the movement takes to the streets, the sectarian samurai poke their spears at police and loot the Body Shop".

In 1984 Campbell suggested that rising unemployment would lead to the criminalisation of young men: "the form of boys' masculinity constitutes them as folk devils, a 'danger to society' ... they generate a kind of moral panic ... symbolised by the social nuisance of big bad boys who bite social workers". Seven years later, though, Campbell lost her critical distance on the criminalisation of young men reporting rioting in Blackbird Leys: "The riots of 1991 were driven not by pain but by pride, the vanity of fragile masculinity... Some of the 'bad boys' have just made some crap estates even worse."

As Campbell's distaste for the mob intensified, her attitude to the forces of law and order softened. Her sympathetic interview with Derbyshire Chief Constable John Newing was titled 'A Fair Cop'.

In September 2008, she applied for membership of the Women's National Commission, a government quango set up to speak on behalf of UK women, and was successful.

In July 2009, writing for The Guardian she wrote strongly in support of surveillance of the public and vetting of authors before allowing them to present to children in schools.

In October 2009, she was announced as the Green Party Parliamentary candidate for Hampstead and Kilburn stating "We put at the absolute centre of our policies, the sustainability of social relationships and the need for a fundamentally fair society. We stand for social justice, respect and equality between the genders and the generations. And we don’t think that slicing public services to ribbons can be the way forward for British society."

In Marxism Today, Campbell protested that, "anyone who respects children's accounts of child abuse aren't taken seriously," and for some reason professionals were reluctant to believe that Satanists were, "organising rituals to penetrate any orifice available in troops of little children; to cut open rabbits or cats or people and drink their blood; to shit on silver trays and make the children eat it."

In 1998 Campbell reported on the Newcastle City Council report into allegations of child abuse at the Shieldfield Nursery in the city in 1993. She claimed the council inquiry was "stringent" and had found "persuasive evidence of sadistic and sexual abuse of up to 350 children." The alleged perpetrators were workers at the nursery, Dawn Reed and Christopher Lillie, who had already been cleared of multiple charges in a criminal trial in 1994. They subsequently successfully sued the Council, the "Independent Review Team" who produced the report, and the local Evening Chronicle newspaper for libel. Awarding Reed and Lillie the maximum possible damages of £200,000 each, the judge in the case made a "very rare" finding of "malice" on the part of the Independent Review Team, in that, "they included in their report a number of fundamental claims which they must have known to be untrue and which cannot be explained on the basis of incompetence or mere carelessness." One of the four people on the Independent Review Team was Campbell's close working partner Judith Jones (see above), who was previously involved in the Nottingham case.

Writing on the Sally Clark case, Campbell rejected any feminist arguments based on the, "suspicion that medical men play God and pathologise women's distress." Such feminist arguments, she thought, ignored women's psychoses, or what Campbell called, "the dangerousness of motherhood: it can make some women lose their minds, it makes some mothers murderous." These speculations about Clark's mental state proved unfounded, however, as she was cleared of murder on appeal. In 2007 Campbell defended paediatrician David Southall, whose involvement in the Clark case was being investigated by the General Medical Council, saying, "David Southall established a gold standard in the detection of lethal child abuse." Southall was struck off the Medical Register for gross professional misconduct.

Campbell has received several citations and awards from British universities. She is an Honorary Doctor of Letters at Salford University, an Honorary Doctor of Letters at Oxford Brookes University and an Honorary Doctor of Letters at the Open University. She was awarded a Simon Fellowship from Manchester University.

Her journalism has gained several awards both for Campbell’s books and newspaper articles. She was awarded the Cheltenham Literature Festival Prize in 1984 for her book Wigan Pier Revisited and the Fawcett Society Prize for her book The Iron Ladies. Campbell was named Campaigning Journalist of the Year by the 300 Group, an initiative to get more women into Parliament founded by Lesley Abdela, and later involving Elizabeth Vallance and Shirley Williams. Her Dispatches documentary "Listen to the Children" resulted in her receiving the Independent Television Producers First Time Producers award.

In June 2009 Campbell was made an OBE. She argued that "by clinging to symbols and rituals that belong to a cruel imperial order the government compromises the gonged" but defended herself on the grounds "getting gonged confers recognition of 'citizens' contributions' to a good society — in my case equality — and the gesture affirms our necessity; the radicals — not the royalists — are the best of the British".