UPDATED 1.15pm The man serving life in prison for killing Featherston schoolgirl Coral Burrows has pleaded guilty to attempted murder after he brutally attacked another inmate at Auckland Prison.

Stephen Roger Williams will be sentenced in March after admitting the violent attack.

The Herald revealed last month that Nikki Roper - also serving a life sentence for murder - suffered life-threatening injuries after an attack on a landing in C Block at the maximum security prison in Paremoremo.

"Roper was stabbed with a piece of glass in the lower neck area," a source said after the December 11 attack.

"He was also stabbed with a broken-off part of a broom handle, through the neck into the chest cavity."

The source said the broom handle snapped, leaving about 20cm embedded in Roper's body.

The Herald was told Williams carried out the attack.

He was later charged with attempted murder.

He appeared in the North Shore District Court for the first time on the charge on December 23.

His case was then transferred to the High Court at Auckland where he entered a guilty plea this morning.

He will be sentenced in the High Court at Auckland in March.

Williams is serving a life sentence for murdering Coral, his stepdaughter, in 2003.

He beat the 6-year-old to death and dumped her body near Featherston.

Roper was jailed for life with a minimum non-parole period of 14 years for murdering Christchurch mother Alexsis Tovizi in December 2010.