Mark Gettleson from the Howard League for Penal Reform said the Government's proposals to give ex-prisoners supervision in the community is "an admission that short-term prison sentences are failing".
He added that prisoners are currently "being warehoused in enormous overflowing prisons, rather than being given something useful to do on the outside."
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Police are trying to find the driver of the car following the incident in Kingfisher Close, Brownhills.
An unnamed man died at the scene, while a woman was pronounced dead after being taken to St George's Hospital, Tooting, south-west London.
Eastern areas will see a few showers coming in on the northeasterly breeze