England need to be "more consistent in training" to reduce the number of errors they are making in matches, says fly-half George Ford.
England lost three of their four World Cup warm-up matches - which included a first defeat by Fiji on Saturday.
England's next game is their World Cup opener against Argentina on 9 September in Marseille.
"We're playing the way we train at the minute, which is not good enough obviously," Ford said.
"We understand that we need to make fewer mistakes. There's an urgency that we need to fix it and get better.
"The way you do that is to be more consistent in training. We're clearly not consistent in training, there are probably too many errors in training."
England have now lost five of their past six games, with head coach Steve Borthwick winning only three out of his first nine in charge.
"We're making too many errors," added Ford. "What the reason for that is I can't be sure. Maybe it is a little bit of over-eagerness or a little bit of inaccuracy, or maybe it is a little bit of understanding.
"It's probably a little bit of all of it, to be honest. But one thing for sure is we can't keep doing it."
'We conceded too many tries and missed too many tackles'
England have dropped to eighth in the world rankings following the defeat by Fiji and are now ranked below Argentina after the Pumas thrashed Spain in Madrid.
Their defence has conceded 30 tries and an average of 26 points in each of their nine games under Borthwick.
"I'm very clear that I was disappointed with the defence. We conceded too many tries and we missed too many tackles," Borthwick said.
"Our focus is on ensuring we are much better than that against Argentina in two weeks' time.
"The dropping off tackles has not been the case with what we've seen recently, but there were a lot against Fiji - more than 20 missed tackles. I think the total was 27.
"Now Fiji have exceptional power and speed, and that hurt us. But what we have to do is look at those tackles and what we could have done better.
"We didn't want that result. We were clearly disappointed by the game and disappointed by aspects of that performance.
"Whilst there are areas of our performance which saw signs of growth, you can't slip off that many tackles in a Test match."
Ford, however, is "more than confident" England will get things right for their opening pool game.
"When it comes to our plan for Argentina and our understanding of what we need to do to win that game, we'll be crystal clear on it," he said.
Vice-captain Ellis Genge posted on X, formerly known as Twitter, following the defeat by Fiji: "Write us off now, all the best" before later adding England understand they are not where they "need to be" right now.
He added: "We will get there, stick with us through the dark, thanks for the love we appreciate it."
Prop Joe Marler, who replaced Genge in the second half, also took to the platform to say the side are "gutted" they could not get the win for Courtney Lawes on his 100th cap.
England also face Japan, Chile and Samoa in their World Cup pool, before a likely quarter-final against Wales, Australia or Fiji.
What led to Hitler's ultimate downfall? Look at the actions taken as the Third Reich faces collapse in the final weeks of World War Two
Where would he like to go for his next food journey? Stanley Tucci spills the beans in his chat with Lauren Laverne