Prime Minister Scott Morrison will order a royal commission into horrific allegations of abuse against people with disability in what will be the sixth judicial probe in Australia in as many years.

In a letter to the nation's premiers and chief ministers, Mr Morrison for the first time confirmed he believes a joint royal commission is the best way to get to the bottom of allegations about the treatment of people with disability.

Prime Minister Scott Morrison has told state leaders he wants a royal commission. Credit:Dominic Lorrimer

"I think we can all agree that violence, abuse and neglect of people with disability is abhorrent and that we should be doing all we can to ensure a safe and secure Australia," Mr Morrison wrote.

"It is crucial that all governments work closely and collaboratively to ensure a holistic response to this issue. Accordingly, I am now seeking your in-principle agreement for the establishment of a joint royal commission and the most appropriate consultation pathways to progress this important matter."