They were sent abroad, often without their parents’ consent. Large numbers were sexually and physically abused, while hunger and neglect were familiar enemies. Their education tended to be poor and they were often forced to perform exhausting manual work.

Between the end of the second world war and 1970, successive UK governments allowed thousands of children, almost exclusively from deprived backgrounds, to be removed from their families, foster carers and care homes to be sent to institutions or families in Canada, Australia, New Zealand and Southern Rhodesia, ostensibly in the belief that they would enjoy a better life. Some 4,000 were sent to Australia, a mass emigration captured in the 2010 film Oranges and Sunshine, which starred Emily Watson as Margaret Humphreys, a social worker from Nottingham who uncovered the scandal.

But for many children, the promised land failed to deliver. Recognition of just how spectacularly the UK had failed them came in 2010 when the then prime minister, Gordon Brown, officially apologised, stating: “We are sorry that instead of caring for them, this country turned its back.”

Eight years on, however, victims complain that their betrayal continues. Despite a government-commissioned inquiry recommending the urgent creation of a compensation scheme, there has been little sign of action, they say. Their lawyers are now taking the first steps in a high court challenge to obtain redress, a legal manoeuvre that threatens to further embarrass a government accused of having failed the Windrush generation.

For some, it is likely to be the last chance for justice. “We cannot sit by, waiting for the government to do the right thing,” said Norman Johnston, president of the International Association of Former Child Migrants and their Families (IAFCM&F).

The action follows the March publication of a report on the children’s experiences by the Independent Inquiry into Child Sexual Abuse (IICSA). Witnesses described “care” regimes which included physical, sexual and emotional abuse as well as neglect. “Some described constant hunger, medical neglect and poor education, the latter of which had, in several instances, lifelong consequences,” the report found. “By any standards of child care, then or at the present time, all of this was wrong.”

Boys from Dr Barnardo’s homes aboard the ocean liner Largo Bay as they emigrate to Australia in 1948. Photograph: Hulton Deutsch/Corbis via Getty Images

A former child migrant said his experiences at one school were “better described as torture than abuse”, and recounted how he was locked in a place known as “the dungeon” without food or water for days.

Another told of “backbreaking” work on the construction of a school building. A third spoke of a failure to give him medical care, which resulted in the loss of an eye. In some places, there were persistent beatings, and one witness described how he had tried to kill himself at the age of 12.

Michael, who was placed with the Christian Brothers in Perth, Western Australia, where he was raped, abused and starved, told the inquiry he felt abandoned by his country. He recounted how one Brother “organised special punishment days for the boys, during which he would make them watch horses being killed”. The children were so hungry they hunted in bins for scraps and on one occasion roasted a cat to eat.

When it published its findings, the IICSA recommended that a redress scheme for all child migrants should start within 12 months – 1 March 2019 at the latest. A similar inquiry in Australia established a redress scheme in little over six months.

In July, Jackie Doyle-Price, the mental health and inequalities minister, confirmed the government intended to give a formal response to the recommendations by the summer recess. But the deadline came and went, according to the IAFCM&F, a delay it says has meant some victims will never receive what the UK owes them. “To date, at least 21 former child migrants are known to have passed away without justice since the report was issued,” said Johnston, who was abused at an Australian Christian Brothers’ home. “For them, for those child migrants who gave their painful testimony before the inquiry, and for those of us still waiting, we cannot sit by waiting for the government to do the right thing.”

Norman Johnston, president of the International Association of Former Child Migrants and their Families, was abused at an Australian Christian Brothers’ home.

Acting for the association, the law firm Leigh Day has sent a Letter Before Claim to the Department of Health and the Home Office, threatening a high court challenge over the perceived failure to respond to the inquiry’s recommendations. The legal challenge threatens to embarrass the government after accusations it was slow to pay compensation to members of the Windrush generation whose status as British citizens was disputed by the Home Office.

“Consecutive governments have let these British citizens down,” said Alison Millar, a partner at Leigh Day. “First as children deported to foreign lands without any safeguards, then as adults left to cope alone with what they had endured and now this government, faced with recommendations from its own inquiry, is letting them down again in their advancing years. Following the shameful delays to establish compensation to help the Windrush generation, this again appears to be a case of putting elderly British citizens at the back of the queue while internal political squabbles take precedence.”

A Department of Health and Social Care spokesman said: “We are carefully considering the findings and recommendations made in the report and will provide a considered response to the inquiry’s recommendations in due course.”