The Prime Minister is expected to slam the "scandalous" failure of the prisons sector today as he outlines his vision for a modern prison system.

Giving the first speech purely focused on prisons by a British Prime Minister in reportedly over twenty years, he will outline plans to give prison governors complete control over the way they run their prisons - which Downing Street claim will empower staff, drive up standards and cut re-offending.

David Cameron will promise six of these new reform prisons by the end of the year and through a new Prisons Bill in the next session, has vowed to unleash these principles across the prisons system.

Mr Cameron will insist that punishment is "not a dirty word" but prisoners must not be allowed to feel that society has given up on them.

In a sign that he is moving Tory policy a long way from the "prison works" mantra of former leader Lord Howard, Cameron will declare that penal reform should be the "great progressive cause in British politics".

But he will acknowledge in some cases there is no alternative to prison.

In the speech in London, he is expected to say: