England hammered Australia by 347 runs at Lord's with a day to spare to go 2-0 up in the five-match series on Sunday. While England is closing in on its third straight Ashes series triumph, the Australians are coming to terms with a sixth straight Test loss for the first time in 29 years. Australia lost seven straight Tests in 1888.
Australia was bundled out for 128 on Friday in good batting conditions, and coped only slightly better in its second innings with 235.
"Our performance with the bat was unacceptable," Clarke said. "The wicket was very good for batting. We had a great opportunity but we let ourselves down. We have plenty of experience in our top seven, and we have seen already on this tour that guys can score runs against this attack. But our shot selection was poor and we didn't have the discipline that England had.
"They were willing to bat for long periods and graft through the tough times, but we certainly weren't in that first innings. There are going to be times when you feel comfortable and you can play some shots and there are going to be other times when the opposition bowl well and you have to back your defense."
Clarke has led the team in five of those six Test defeats. While he is unfortunate that many of the great names of recent generations - such as Ricky Ponting and Adam Gilchrist - have since retired, he still knows the team is capable of better as it copes with a period of transition.
Conversely, England captain Alastair Cook is enjoying his team's success. It has won all four Tests so far in the English summer to close in on South Africa at the top of the world rankings.
But Cook said he is not considering a 5-0 whitewash, as Australia inflicted on England in 2006-07.
"It's too early for that," Cook said. "You only have to look at our dressing room to see how hard we've had to work to win these two games.
"You (the media) can think all you want (about 5-0), but we know how hard it is going to be the next few games."