Aaron Finch won the toss then watched his side crumble to 3-30 at the end of the fifth over, when Steve Smith took off for a single that was never there and was found well short of his ground by Eoin Morgan's direct hit.

Finch top-scored with 40 as the tourists scrapped together a total of 7-157, but Jos Buttler made a mockery of that target in 18.5 overs.

Buttler crashed a career-best 77 not out, securing victory in authoritative fashion when he danced down the pitch and slapped a delivery from Adam Zampa back over the legspinner's head for six.

The T20 series finale starts at 3am AEST on Wednesday, when Australia risk relinquishing their No.1 ranking in the shortest format.

"We were just that little bit off, which I think you get from playing cricket," Starc said.

"It's just that match intensity. International cricket is always going to be a step up.

"You can't really simulate international matches just by having net sessions or centre wickets.

"It's not an excuse. We've had plenty of preparation here."

England are match-hardened at the end of their home summer, while Australia are coming off a coronavirus-enforced break dating back to March 14.

The tourists have so far used 11 of 21 players in their enlarged squad.

"We'll sit down and talk about that (potential changes). Being not all that far out from a T20 World Cup, it's important to keep drilling your basics and keep drilling your best XI," Finch said.

Morgan, who was full of praise for Buttler plus express pacemen Jofra Archer and Mark Wood, suggested England's best XI would pursue a 3-0 series win.

Morgan's biggest concern was a dislocated finger he suffered while fielding, when Marcus Stoinis hammered a full toss straight at him at cover.

"It's just sore ... we'll see how it is in the next couple of days," Morgan said.

Finch was left cursing a middle-order collapse of 4-9 in the series opener, during which Australia eased to 1-124 after 14 overs then inexplicably capitulated in pursuit of 163.

England required 18 runs from their final two overs - a similar scenario to what confronted Australia two days earlier - but sixes from Moeen Ali and Buttler meant this match didn't enter its final over.

Debate about whether Buttler is better suited to opening or finishing will continue.

The dashing keeper-batsman performed both roles against Australia, hitting 10 boundaries after snaffling edges offered by David Warner, Alex Carey and Glenn Maxwell.

"Jos is a world-class player and if you don't get the guy who is opening out, you won't win," Finch said.

Australian Associated Press