NSW prison probe into 'bashing' cover-up

A NSW prison officer has told a corruption inquiry he warned his colleagues "that's enough" as they continued to wrestle an inmate subjected to unwarranted force.

Wesley Duffy was one of several guards present in a cell at Lithgow Correctional Centre when the alleged incident happened in February 2014.

Appearing before a corruption inquiry in Sydney, Mr Duffy recalled warning his colleagues "that's enough" when two of them - Terrence Walker and Elliot Duncan - continued to wrestle the man, despite his acquiescence.

The Independent Corruption Against Corruption is investigating allegations the officers later lied in official reports, deleted CCTV and planted drugs to justify a cell search.

An official report about the incident, which left the inmate with a black eye, bruising to the mouth and injured ribs, said he tripped and fell on a toilet while trying to flush contraband.

Mr Walker has admitted the report was "all lies" and also claimed Mr Duffy was excluded from the collusion because other guards anticipated he would want to be honest.

Mr Duffy said he distanced himself from the group when he realised they were submitting false statements.

The inquiry before Commissioner Stephen Rushton SC continues.