The Bafta- and Golden Globe-winning actor Samantha Morton, who spent much of her childhood in a succession of children's homes in Nottingham, has revealed for the first time that she was sexually abused by residential care workers and said she believes abuse was "rife" within the city's children's services.

In an exclusive interview with the Guardian, Morton said she had reported one particular incident, in which two men jointly abused her when she was 13, to Nottinghamshire police and social services shortly after it happened, but no formal investigation was undertaken by either agency. The men were allowed to stay in their jobs, while she was abruptly moved to another home.

She said she was recently shocked to be told by police that her records from the time contained only a reference to "frolicking", rather than recording the serious child abuse allegations she had made.

The actor had chosen to speak out, she said, after it emerged last month that an estimated 1,400 children had been sexually exploited in Rotherham between 1997 and 2013. "I just wanted to go public with this, to say, we know it's rife but why are there not further investigations into other areas? It isn't just Rotherham, I'm sure it's not just Rotherham," said Morton.

On Friday the widespread scale of alleged child abuse in Nottingham became clear when it emerged that 95 claims of abuse at 13 separate children's homes have been submitted to the city and county councils, while police investigations into five homes are ongoing.

The councils have already settled civil damages claims totalling £250,000 with 26 former residents of the Beechwood home in Mapperley, Nottingham, without admitting liability.

Morton spent time at Beechwood but says she was not abused there. At least three other homes where she was housed during her childhood are the subject of abuse allegations.

The actor, 37, who has twice been nominated for an Oscar,and starred in the blockbuster Minority Report alongside Tom Cruise, was first taken into care as a baby and spent the rest of her childhood in and out of foster care and children's homes. She had told social workers about "all sorts of sexual abuse that happened to me from a very, very young age", she said, but no action had ever been taken. She described one incident when she was 13 when two male members of staff at the Redtiles home came into her bedroom at night, removed her nightclothes and abused her. She was initially embarrassed but eventually told social workers, who did nothing. "There was no support, no offer of counselling, no wanting to delve deeper ... Maybe they just assumed I had been abused already, or was being, anyway." She estimates that 90% of her friends in the home had been sexually abused, though not all by staff.

A few weeks later Morton told her mother, who took her to a local police station. Again, no further action was taken.

She said police officers suggested their hands were tied because the assaults were taking place within the social services system. "A lot of people who abused my friends were people in very, very top jobs within the social services. Nottingham in the 80s was rife with that."

Morton recently contacted Nottinghamshire police to ask what information was on file relating to her complaint as a 13-year-old, to be told her notes recorded no mention of sexual abuse. "I said that I was shocked and didn't know what to say," she said.

The Guardian later learned that the records referred to allegations of "frolicking", a term which an officer confirmed to Morton had been recorded at the time.

"I asked her what that meant. No answer. I said I didn't remember saying that and I can't imagine saying that at 13 ... Even now it's not something I would say."

In a statement, Superintendent Helen Chamberlain, head of public protection at Nottinghamshire police, said she had spoken to Morton at length. "But as yet she has not given enough to suggest a criminal offence nor stated that she wishes to make an allegation about an offence. We will continue to work with her and if she decides to report an offence she can be assured that we will investigate it fully, working closely with the local authority, and seek to take action, where appropriate."

Morton said she was "heartbroken" by the police response. She said and that she had described the incident to Chamberlain and stressed that she wanted to take it further. "If that isn't a criminal offence against a child I don't know what is."

Steve Edwards, service director for children's social care for Nottinghamshire county council, which had responsibility for children's services while Morton was in care, said the council was hoping to speak to her: "We are hoping in the near future to speak with Samantha so that we can fully understand her concerns which date back to 1991. "Nottinghamshire county council takes all allegations of abuse, whether current or historic, extremely seriously."

Asked what she believed should change, Morton called for an end to the privatisation of children's services, higher standards for residential care workers , a reversal of cuts to the care system and a legal requirement for people in authority to report abuse when they suspect it.

Peter Wanless, CEO of the NSPCC, paid tribute to Morton for speaking out and called for a culture change across social services, "so that children are listened to and taken seriously, not dismissed as troublemakers". He echoed Morton's call for mandatory reporting of suspected abuse in institutions which have a responsibility for the welfare of children.