President Barack Obama has called for criminal justice reforms including curbing the use of solitary confinement and voting rights for felons.

The president said lengthy mandatory minimum sentences should be reduced – or thrown out entirely.

“Mass incarceration makes our entire country worse off, and we need to do something about it,” he said.

Barack Obama urged Congress to pass a sentencing reform bill by the end of 2015.

On July 16, Barack Obama will be the first sitting president to visit a federal prison – part of week-long focus by the White House on the criminal justice system.

Speaking to a gathering of the National Association for the Advancement of Colored People (NAACP) in Philadelphia, Barack Obama discussed investments in education, alternatives to trials and prison job training programs.

US Attorney General Loretta Lynch has been tasked with reviewing the overuse of solitary confinement, Barack Obama said.

“Do we think it makes sense to lock people up in tiny cells for 23 hours a day? It won’t make us safer and stronger.”

The US should not be tolerating overcrowding in prisons, gang activity or rape, which Barack Obama called “unacceptable”.

Criminal justice reforms have been a subject of rare agreement between Republicans and Democrats in Congress.

He noted that African Americans and Latinos disproportionately make up most of the prison population.

On July 13, Barack Obama commuted the sentences of 46 prisoners, many of whom were serving time for non-violent drug offences.

“If you’re a low-level drug dealer, or you violate your parole, you owe some debt to society … but you don’t owe 20 years,” Barack Obama said.

The president said for what the US spends on keeping people in prison per year, $80 billion, there could be universal pre-school, doubled salaries for high school teachers or free tuition at US public colleges or universities.

This week’s focus on criminal justice signals a renewed bid by Barack Obama’s administration to tackle what he sees as a lack of fairness in the system.

“Communities that give our young people every shot at success, tough but fair courts and prisons that seek to prepare returning citizens to get that second chance…That’s what we’re here to build,” he said.

The last significant changes to the criminal justice system in the US came in 2013 when Attorney General Eric Holder dropped mandatory minimum sentences for non-violent drug offenders.