Frustrated England must be united

England must stay "united" and focus on next weekend`s "knockout" World Cup game with Australia after losing to Wales, says boss Stuart Lancaster.

The hosts squandered a 10-point lead as Wales won 28-25 at Twickenham, and defeat on Saturday could all but end their hopes of qualifying from Pool A.

"We`ve got a massive game now to build to," said Lancaster.

"There`s a lot of frustration in the changing room and that frustration has to be turned into a positive mindset."

England, who led 22-12 early in the second half against Wales, have been criticised for the ill-discipline that allowed Dan Biggar to kick his side back into contention.

Biggar succeeded with all eight of his kicks, seven of which were penalties - including a 50-metre effort that put Wales into the lead in the final minutes.

Lancaster said he was "hugely disappointed" after letting a winning position slip.

"We gave a couple of penalties away which allowed Wales to build belief and momentum. Wales did well to score the points at the end and we didn`t close out the game," he said.