Porte led by 20 seconds going into the penultimate 151.5 kilometres stage today, which included two climbs up Willunga Hill and took riders through the McLaren Vale wine region.

The BMC team leader got the better of his closet rivals with a devastating attack over 1km from the finish.

His compatriot Nathan Haas and Colombian Esteban Chaves who took third.

Porte now leads Chaves by 48sec before Sunday’s last stage in Adelaide, the biggest lead ever for a Tour Down Under heading into the final stage.

Porte, racing for the first time since he crashed out of the Rio Olympics road race five months ago, said the Tour was his first goal of the year but his major aim is a podium finish at the Tour de France, after last year’s fifth place.

The Australian arrived at the bottom of the climb alongside his main rivals after the peloton reeled in those who broke away in the early stages of the race.

Team Sky initially set the tempo at the bottom for Sergio Henao, but Porte began to accelerate with around 2km remaining.

Haas and Chaves made efforts to keep apace, but were no match for Porte's power and speed who cruised away from the rest of the field with around 1km to go.

It was the 13th consecutive stage win by an Australian at the Tour Down Under and what will be the fourth consecutive overall victory for nation should Porte safely navigate tomorrow's stage.

“I tell you what, that hurt more than the other three I’ve won up here,” Porte said.

“It was incredible teamwork today.

"This is not an easy climb – to win it is great for morale.

"For me, the biggest goal this year is July, the Tour de France, and things are going well.”

Well before the start of today's climb, Spaniard Gorka Izaguirre had lost touch with the leaders, costing him his second place in the overall standings.

The Movistar rider attained some nasty injuries after he was caught in a three-rider crash on Thursday near the Victor Harbour finish.