All convicted male prisoners are to be banned from watching violent and sexually explicit films as part of a crackdown on "perks" that comes into effect today.

Inmates will also be required to wear a uniform for their first two weeks behind bars, and will lose automatic access to daytime television and gym equipment.

The changes to the prison service's incentives and earned privileges regime have been ordered by the justice secretary, Chris Grayling, and will apply across England and Wales.

The requirement to wear prison clothes and restrictions on access to private cash will be compulsory for all convicted prisoners for the first fortnight of their sentence as part of a new "entry level" to the system. Female prisoners will not have to wear a uniform. In most cases the uniform will involve a grey or maroon tracksuit with a light blue T-shirt. In some jails older uniforms with a striped top will be worn.

Grayling has said that under the new policy a lack of bad behaviour will not be enough to earn privileges. Instead inmates will have to work actively towards their rehabilitation and help other prisoners.

The justice secretary has been particularly exercised about access to television for prisoners. The 4,000 inmates in privately run jails will not be able to watch Sky Sports or other subscription channels that are not available to public sector prison inmates.

All prisoners are to be banned from watching daytime television when they should be doing purposeful activities.

Prison governors have been working to make staff and prisoners aware of the changes since April to ensure the scheme is implemented safely.

Earlier this week Vicky Pryce, who was jailed along with her ex-husband, the former cabinet minister Chris Huhne, warned that there could be rioting when the changes come into effect. "There's very little else to do in prison but watch television. It's one of the very few things that these people have," she said. "And if they take those away from their cells, as the government is saying it will do now, there will be riots, serious riots. And that is not an overstatement."

But Grayling defended the changes saying: "For too long the public has seen prisoners spending their days languishing in their cells watching TV, using illegal mobile phones to taunt their victims on Facebook or boasting about their supposedly easy life in prisons. This is not right and it cannot continue."