England warmed up for last autumn's Cook Cup clash with a 54-12 rout of Fiji, but when it came to facing the Wallabies a week later they were off the pace.
They slumped to a 20-14 defeat to a side that had been humiliated by France seven days earlier and Lancaster insists they must produce from the very start of their opening autumn Test.
"The key message this week is we can't wait a game or two into a series to get up to speed," England's head coach said.
"Being an international rugby player is being ready in the here and now
"You must get to that level of intensity that is required to win without going through one or two poor performances or needing a kick up the backside."
The countdown to the 2015 World Cup begins in earnest this autumn with fixtures against Argentina and New Zealand scheduled after Australia.
Lancaster enters the series with the expectation that England will win all three games as he searches for the consistency that will bring success.
"It's a defining year because we're two years out from the World Cup and we have got consistency in the coaching team and in terms of selection," he said.
"We've had some good experiences and some not so good, but the good have outweighed the not so good. It's a matter of building on those now.
"We've won seven out of the last eight games, but we've not consistently delivered in every game.
"The next step is to consistently deliver in every game at the highest level. Australia have been ranked in the top three for the last three or four years.
"It's a big game but one we're ready for and one we should be expecting go into with confidence.
"Alongside Argentina and New Zealand, we'll have to go into the game with the expectation of winning."
Meanwhile, members of England's 2003 World Cup-winning squad will gather at Battersea Evolution on Friday night for the official 10-year celebration dinner.
A decade after captain Martin Johnson lifted the Webb Ellis Trophy, the majority of the players involved in English rugby's finest hour will be honoured at the gala event.
The dinner, hosted by Martin Bayfield, will see players and management recall their memories of the tournament.
Only five members of the squad - Jonny Wilkinson, Julian White, Joe Worsley and Mike Tindall - will be missing with all but White unavailable due to playing or coaching commitments.
The event has been organised by the Rugby Football Union and also includes an auction for the Injured Players Foundation and Restart charity.