He called on ministers to ensure no-one was "left idle in their cells" but presented with "full, purposeful and active days, which are the only things that are going to enable them to live useful and law-abiding lives".
When demand for the plant's batteries didn't meet expectations, the company filled orders with cells made at a factory in South Korea, leaving the Michigan plant largely idle, according to the report by the Department of Energy's Inspector General, Gregory Friedman.