Australia are 3-1 down in the series after a humiliating fourth Test drubbing by an innings and 78 runs at Trent Bridge when the tourists were bowled out for 60 before lunch on the first day.
"We have been poor, we have been outplayed by a superior opponent, and as coaching staff, players and selectors we fully accept the blame for our losses at Edgbaston and Trent Bridge," Lehmann said in a column for the Cricket Australia website.
Lehmann attacked the suggestion that the players' wives, partners and families who had accompanied them on this tour had somehow contributed to the their lack form on the field.
"There's no question we haven't performed as we expected and we appreciate that in those circumstances we have to accept negative criticism from the media because we've had so much positive coverage during our success over the past two years," he said.
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Lehmann said the reality of international schedules was that some in the squad would have only been home for three or four days since the Boxing Day Test last December.
"I can't think of any other sport in which the players are away from their homes and their loved ones for such long stretches of time," he said.
"And as such we will continue to welcome families as part of any tour because it is simply unrealistic to expect them to spend those long periods apart."
"Michael is one of our most committed trainers who will go to the nets every day even when we have optional sessions or give guys a day off, and on practice days he'll travel to the ground early with the support staff who go ahead to get everything set up," he said.
He said the team hoped to send off Clarke with a win.
"From there, we enter a new era of Australian cricket that everyone in our set-up is really excited about," he added.