Jay-Z has thrown his support behind a campaign to reform the US criminal justice system.

The 49-year-old rap star - who is married to singer Beyonce - has joined forces with Meek Mill, as well as sport and business leaders in the US, to overhaul the current approach to criminal justice in the States.

The Reform Alliance's mission is to dramatically ''reduce the number of people who are unjustly under the control of the criminal justice system, starting with probation and parole''.

The campaign group - which says it wants to help people who are ''trapped in the system'' - added: ''To win, we will leverage our considerable resources to change laws, policies, hearts and minds.''

The group of high-profile figures have agreed to collectively raise as much as $50 million in the hope of freeing one million prisoners in five years' time.

Meek, 31 - whose real name is Robert Williams - recently spent time in prison for a minor probation violation.

In 2007, the rap star was arrested for drug and gun charges and in 2009, he was sentenced to between 11 and 23 months in prison.

Meek - who has always denied the original charge - was then found guilty of violating the terms of his parole in 2014, when he was accused of using cannabis, leading to a spell in prison.

And in 2017, he was found guilty of violating his parole once again, meaning he was sentenced to two to four years in state prison, before he was released prematurely in 2018.

Jay previously spoke about Meek's case in an article for the New York Times newspaper.

He wrote: ''What's happening to Meek Mill is just one example of how our criminal justice system entraps and harasses hundreds of thousands of black people every day.

''I saw this up close when I was growing up in Brooklyn during the 1970s and 1980s. Instead of a second chance, probation ends up being a land mine, with a random misstep bringing consequences greater than the crime. A person on probation can end up in jail over a technical violation like missing a curfew.''