Alexis Jay officially retired two years ago – not that you’d notice. In 2013 she stepped down from her role as Scotland’s chief social work adviser, shortly after being awarded an OBE. But rather than tending to her garden she ended up digging up horrific claims of child sexual exploitation in Rotherham. That job done, the scalps of many officials taken, she moved on to sort out Northern Ireland’s safeguarding children boards.

But last week the 66-year-old began her biggest task yet, when she joined the panel of what has been described as Britain’s most complicated and wide-reaching statutory inquiry ever. The independent inquiry into child sex abuse (IICSA) is expected to take five years investigating claims of abuse in faith and religious organisations, the criminal justice system, local authorities and national institutions such as the BBC, NHS and Ministry of Defence.

Jay was one of the first names confirmed as part of the panel. So mammoth is the task that last week the government committed £17.9m to cover the next year of the inquiry alone. “I think it’s very complex and I don’t under-estimate the scope of the inquiry. It’s huge. Very wide ranging,” she says, when I meet her in Glasgow.She is under no illusions about how tough the new gig is – not least because the inquiry had such a rocky start, losing the support of victims very early on, along with its first two chairs, who were found to be too close to the establishment figures they would be investigating. But Jay, who is a visiting professor at the University of Strathclyde’s Centre For Excellence For Looked After Children, insists she is determined. “I am passionately committed to it taking place and to the victims and survivors, and to get justice and truth out of the process,” she says.

Almost a year on from the televised press conference at Rotherham football club that made her name, Jay still can’t believe the rumpus her report caused. Taking her place in front of a cluster of microphones last August with a leopard-print iPad, she read out a statement to the assembled press corps revealing that, by her conservative estimate, 1,400 children had been sexually exploited in Rotherham over a 16-year period.

“By victims we are not talking about children who were at risk of sexual exploitation, who were friendly with victims or who moved in the same circle,” she told the journalists. “The 1,400 victims are those who had actually experienced sexual exploitation.” Determined that no one could bat away her findings, she had produced a 153-page report that spelled out in plain language the appalling abuse suffered by children aged 10-16 in the South Yorkshire town between 1997 and 2013.

Her findings dominated the headlines for days, and she fielded calls from the New York Times and TV stations in Australia asking detailed questions about South Yorkshire. “I knew it was going to be significant, but not quite on the scale it was,” she admits.

For victims, she represents the hope that the statutory inquiry will not be another whitewash. Each week she still receives phone calls, emails and letters from survivors who come to her, rather than the police, to tell their stories.

The reverberations from her inquiry were far-reaching: in February a team of independent commissioners was brought in by the then communities secretary, Eric Pickles, to run the council, after it was deemed “unfit for purpose”. Jay was only minutes into her press conference when a note was passed to her to say that Roger Stone, the all-powerful Labour leader of the council since 2003, had resigned. He then quit the party and made a somewhat belligerent appearance in front of the home affairs select committee, in which he attacked Jay for making accusations, that were “mostly vague and unsubstantiated”.

Jay laughs in despair at Stone’s apparently wilful blindness. “I am at a loss to know what other evidence people need,” she says. “If that’s how he sees it, so be it. I’m not getting into an argument with him about it. For goodness sake. Would he like to look at every single one of the 937 cases we were given by his council and the police to examine? It might be enlightening.”

Despite spending her whole career dealing with some of the bleakest scenarios imaginable, Jay laughs easily and is disappointed to be told to look serious by the photographer. “No one wants to take a picture of me smiling any more,” she tells me afterwards.

Born in Edinburgh in 1949, Jay had a hard start in life. Her father, a carpenter, died in an industrial accident on Leith docks when she was just two, leaving her mother, a bookbinder, to raise her and her brother alone. “We were very much a working-class family,” she says. “I don’t come from a background of privilege or with any links to the establishment, shall we say.” Her earliest memories are of the cramped tenement the family occupied. “When I was very little we lived in what we call in Scotland a room and kitchen. There was a shared toilet and washing facilities, no bathroom,” she says.

She wanted to be a journalist, and, after leaving school, worked for the now-defunct magazine, Scotland, but soon discovered a passion for social work, and decided to study for a degree on the subject at Moray House School of Education, now part of Edinburgh University. It wasn’t that she was necessarily a bad journalist, she insists: “It was more I didn’t think I was going to be good enough at it.”In her early 20s she fell in love with a fellow social worker, Chris Jay, who already had three children. She has never had children herself, but went on to marry him after the couple moved to Glasgow, where he was deputy head of social work for the now defunct Strathclyde regional authority. She spent six years in some of Glasgow’s poorest areas, working with the first Women’s Aid refuge on the Gorbals, before rising through the management ranks. During her tenure as the chief inspector of social work, she oversaw investigations into allegations of ritualistic sex abuse in the Western Isles and social services’ failure to monitor Colyn Evans, a teenage sex offender who grew up in care and went on to kill 16-year-old Karen Dewar in Fife. She accepted the Rotherham job without hesitation: “I said, absolutely, it’s just up my street.” She had never even been to Rotherham, but that was a plus point. “They needed somebody with no contacts with Rotherham council,” she says.

When she wrote the report, the chapter that gave her the most sleepless nights was about the ethnicity of the perpetrators. Almost all of them were from Rotherham’s Pakistani-heritage community, which makes up just 3.1% of the local population. She cringes slightly when I ask her to explain the overrepresentation. “It’s a very complex issue and I am not an expert,” she begins. I say that she is surely more of an expert than almost anyone else. There’s a long pause. “I understood that the community in Rotherham were described as coming from possibly three villages in Kashmir, and that this identification was very important to them. Their traditions and relationships, these were not sophisticated, they were very traditional. I was told by many people that previous generations had a different view about women’s place in their culture and their society that certainly wouldn’t accord with any sense that we have.”

Nazir Afzal, chief crown prosecutor for the north-west and the Crown Prosecution Service (CPS) lead on child sexual exploitation, explained the overrepresentation of Pakistani men in on-street grooming crimes by pointing to the fact they are more likely to work in the night-time economy in Rotherham. “I’m sceptical about that, not for a principled reason because I haven’t done the research, but from my gut,” says Jay. “I think it presents an opportunity but it doesn’t present a motive. There are many people involved in the night-time economy who don’t abuse.”

Much of the reporting around the Jay report said she had accused Rotherham council and police of failing to tackle sexual exploitation because of a misplaced political correctness. Yet Jay, quite deliberately, never used that term. “I have an aversion to phrases like that,” she says. Instead, she believes the Labour-dominated council turned a blind eye to the problem because of “their desire to accommodate a community that would be expected to vote Labour, to not rock the boat, to keep a lid on it, to hope it would go away.

“There are some people who can only see it as being one massive conspiracy with a single person at the centre of it. That’s not the case,” she says. “It’s not possible, because these organisations and people were too disconnected. They were connected at a professional level, but they had different agendas.”

And what of the victims? Does she have faith that their abusers will be brought to justice? She pauses. “Oh, I don’t know. I do hope so. How would I know? I’m not a criminal investigator.” She has been helping the National Crime Agency, which is conducting a special investigation into Rotherham. Meanwhile some women are still living in fear on the same streets as their perpetrators, I say. She looks sad and gives an honest but depressing answer. “I know, it’s awful. Awful. Let’s see what the NCA can do with it. I would say my confidence is middling. I could not say with absolute confidence that some of the worst perpetrators would be brought to justice.”