South Sydney down Storm 20-10

South Sydney are one win away from a grand final berth after some staunch defence and a helping hand from the video referee delivered a 20-10 NRL qualifying final win over reigning premiers Melbourne at ANZ Stadium.

The Rabbitohs ran out comfortable three-tries-to-two winners to book a preliminary final berth in a fortnight, but they were spared what would have been a frantic finish when the man in the video box intervened to deny Billy Slater his second try of the night.

Trailing 14-6 with 16 minutes remaining, the Storm were coming home hard when a Cooper Cronk kick was spilled by Nathan Merritt, with Slater pouncing on the loose ball to score.

Referee Jared Maxwell awarded the four-pointer only for video official Bernard Sutton to take the try off the Storm, ruling Will Chambers had impeded Merritt in the contest for the ball.

It was a body blow to the Storm's charge - the knockout punch coming three minutes later when Greg Inglis danced his way past a few defenders before finding Issac Luke to make it 20-6.

The Storm fired a last shot when Will Chambers crashed over but it was all too late - the South Sydney defence which had held for much of the game rewarded with a deserved victory, their first over the Storm in Sydney since 2004 and just their fourth finals win since 1971.

It leaves Melbourne to face the winner of Sunday's Canterbury-Newcastle elimination final in a sudden-death semi-final next weekend.

The Rabbitohs can put up their heels, having taken advantage of their chances in the opening period before leaning on a defence which had been carved up last week by the Sydney Roosters to take a 14-0 halftime lead.

It was a nervous Bunnies side early with a penalty and early Sam Burgess knock-on, but Burgess repaid his team when he came up with the hit which forced Justin O'Neill to spill the ball - Adam Reynolds spreading it to an unmarked Farrell to cross out wide.

Lima got over the line through sheer will power as the Storm's discipline went out the window via five straight penalties, Sisa Waqa denied a reply when Farrell held him up in the in-goal just before the break.

It was a different Storm after the break with Slater scoring off the back of a scrum win, but when he was denied a second, it was all over for the visitors.

The Storm will be hoping for some good news on Waqa after he fell heavily on his head late in the contest in an incident which saw Farrell placed on report.

Earlier, Souths prop Roy Asotasi was placed on report for a questionable crusher tackle on Jason Ryles.

AAP