Young offenders will have their cell lights and televisions turned off at 10.30pm sharp to enforce earlier bed times, the justice secretary, Chris Grayling, has ordered.

The restriction, affecting those aged 15 to 17, is aimed at imposing stricter discipline on inmates and to prevent them from staying up all night watching programmes.

"The public expects that serious offenders face prison," said Grayling. "That is right. But it is also crucial that young people, most of whom have had chaotic and troubled lives, finally get the discipline so badly needed to help turn their lives around.

"In some prisons, young people are allowed to go to bed when they please. I don't think that is right. Stopping this inconsistency and introducing a strict, lights-out policy is all part of our approach to addressing youth offending. Those who fail to comply will face tough sanctions."

According to recent figures, there are 827 young people serving custodial sentences in five young offender institutions in England. The changes will come into effect on 3 August.

Those who disobey the new bedtime rules will lose privileges such as access to a television. Young offenders already have to be in their cells by 8pm; some cells, however, contain televisions. Under current regimes, governors have discretion about when lights and TVs should be turned off.

Responding to the new rule, Juliet Lyon, director of the Prison Reform Trust, said: "A new lights out policy will only exacerbate the problem of overuse of physical restraint in the youth secure estate which indicates a lack of trained, experienced staff with enough time to supervise and support the challenging children and young people in their charge.

"As most parents of teenagers know, commonsense discussion, constructive activity, setting reasonable boundaries and encouraging personal responsibility, all work better than new hard and fast rules backed by petty restrictions and harsh punishments."