It's the last straw for Labour; the party wants Serco's prison contracts terminated immediately, after seeing footage of a Mt Eden guard fighting with an inmate.

LISTEN ABOVE: Labour MP Kelvin Davis talks to Newstalk ZB's Michael Sergel about the latest CCTV footage of a security guard fighting an inmate at Mt Eden Prison.

Serco has confirmed it's suspended a staff member, who was caught on CCTV.

It's the latest in a string of controversies, and Labour's Corrections spokesman Kelvin Davis is demanding action.

"This is just evidence of what we've been saying - that Serco has totally lost control of Mt Eden Prison and they really need to be kicked for touch."

The Department of Corrections has resumed control of Mt Eden, after allegations of fight clubs and inmate violence.