Oliver Curtis, husband of PR CEO Roxy Jacenko, has been put it into lockdown in his jail for 24 hours, the Daily Telegraph reports.
The investment banker, 31, was reportedly involved in a verbal altercation with another inmate, described as a "small-time crook", in the common area of Cooma Correctional Centre.
“Another inmate stepped in to calm things down before all three of them were locked down in their cells for 24 hours as a warning,” a prison source said.
“That is not the sort of behaviour that will be tolerated.”
A Corrective Services NSW spokeswoman confirmed the incident.
"Staff separated three inmates after a verbal argument between the inmates at Cooma Correctional Centre last month. There were no injuries."
The Daily Telegraph report that this is an "uncharacteristic" breach of prison rules for the investment banker and father of two.
Curtis is currently serving a 12 month sentence for insider trading.