Building giant "Titan" prison complexes will lead Britain towards a "American-style" justice system, a leading US civil rights lawyer will warn today.
Professor Bryan Stevenson, from New York University, will say Britain risks copying the "damaging and discredited" US system.
The costly 2,500-place prison "warehouses" will undermine efforts to rehabilitate offenders, he will say.
In a lecture to the Prison Reform Trust entitled "Warning from America: the social and economic impact of over-incarceration and how to avoid it" he will say Britain should learn from America's mistakes.
He will say: "This is a time when fear and anger about crime and security is very high which is why our thinking about crime policy has to be sober, sensible and effective.
"The US has made serious mistakes with its criminal justice policy over the last 35 years, the UK should learn from these mistakes, reject the idea of Titan prisons and pursue cost-effective, humane and responsible strategies that avoid mass incarceration and inspires hopefulness rather than the inevitability of imprisonment which has so devastated many American communities."
Juliet Lyon, director of the Prison Reform Trust said: "In fairness to victims we should be helping people break free from addictions, stop binge-drinking, diverting the mentally ill into proper healthcare and making sure that petty offenders do community service to pay back for the harm they have done, not building super-sized prisons.
"It is shaming enough to be the greatest incarcerator in western Europe without slavishly copying America's failing prison system."
Three Titan prisons are planned for London, the West Midlands and the North West by 2014.