Australia have defended a paltry 180 in the second ODI against England in Melbourne, securing a dramatic 21-run win that gives them a crucial early lead in the women's Ashes.

After comfortably winning the series opener in Sydney on Sunday, Australia were in danger of slumping to a heavy defeat on Tuesday when they collapsed to their lowest score batting first on home soil since 2009.

But on a Junction Oval pitch providing plenty of assistance for the bowlers, Australia rallied through spinner Alana King (4-25) and Irish-born seamer Kim Garth (3-37) to bowl England out for 159 in the 49th over.

King, who claimed her best ODI figures, came seriously close to taking a hat-trick when she beat the bat of Lauren Filer the ball after dismissing Charlie Dean and Sophie Ecclestone.

But the 29-year-old's most important wicket was superstar batter Nat Sciver-Brunt, who made 35 and was always going to be the key to England's fortunes in the run chase.

Keeper Amy Jones (47 not out from 103 balls) threatened to lift England to victory after she was dropped by Australia star Ashleigh Gardner on 21.

Jones tried to hit all the runs herself, as she refused to take singles and allow Australia to bowl at her lower-order partners.

But Jones forgot to run on the last ball of the 48th over, with No.11 Lauren Bell then bowled by Megan Schutt off the next delivery to end the game.

"Pretty bloody stoked we got the job done," King said.

"We never back down, no matter when our backs are against the wall.

"We definitely did have our backs against the wall with a sub-par score."

Australia go up 4-0 in the multi-format series, with each of the three ODIs and T20s earning the winner two points, and the day-night Test at the MCG worth four.

"It's a brilliant start to the series and I'm pretty happy to be in the Australian shirt with a 4-0 lead," King said.

It was a dramatic turnaround for Alyssa Healy's team after they fell into trouble on Tuesday when they were sent in to bat by England captain Heather Knight.

Cruising at 1-92, Australia then lost 9-88 as they were undone by spin, with England star Ecclestone (4-35) and Alice Capsey (3-22) running riot.

Australia were bowled out in the 45th over, with only King (13) reaching double figures of the batters six-to-11.

Star allrounder Ellyse Perry (60 off 74 balls) made the only sizeable contribution, boosting England's chances of levelling the series as they aim to win the Ashes for the first time since 2013.

"It's a game that we got ourselves into a position to win and we let go," Capsey said.

"We've missed a real opportunity to get two points on the board, so I think there'll be severe disappointment within the group."

Australia lost 4-7 in 27 balls during the middle of their innings, with the key wickets of Annabel Sutherland, Gardner, Perry and the out-of-form Tahlia McGrath all falling.

Vice-captain McGrath's spot is in jeopardy, scoring just 463 runs at 22.04 in international cricket since the start of 2024.

Young opener Georgia Voll, who starred when she filled in for injured captain Healy against India recently, is patiently waiting for her next opportunity.

The third and final ODI takes place in Hobart on Friday, with the T20 segment of the Ashes starting on Monday in Sydney.