The number of people refused bail and then later found innocent has risen by 30 per cent since 2014, with more than 200 people, including 21 children, forced to wait in prison for sometimes more than a year before being acquitted.

The imprisonment of innocent children is "unimaginable," Child Abuse Prevention Services' Tracy McLeod Howe said.

"It's never ok to incarcerate a child. We know that incarceration only perpetuates an underlying problem. What we would hope that in NSW we will start to see a much more empathetic and positive response to young people who commit offences," she said.

Of the 204 innocent people who had been refused bail in 2018, stays stretched past 500 days for some adults in the District Court, the latest NSW Bureau of Crime Statistics data shows.