West Ham joint-chairman David Sullivan has warned manager Slaven Bilic his side needs to improve.
Sullivan voiced his frustration after the Hammers were beaten 3-2 by a Bournemouth side previously without a win in 2017.
Joshua King grabbed a hat-trick, including a last-minute winner, after Michail Antonio opened the scoring for the visitors and Andre Ayew made it 2-2.
And Sullivan has made it clear he wants to see better when West Ham host Leicester next weekend.
"I was very disappointed and frustrated with the manner of our defeat at Bournemouth on Saturday," said Sullivan on the club's official website.
"We went down there determined to bounce back from the Chelsea game, but we didn't play as well as we know we can.
"Slaven, the players and the staff all know we have to do better.
"We have conceded too many goals early in halves in recent games and, while we've managed to get ourselves back into games like the ones at Southampton and Watford and at home to West Brom, there will be matches where we cannot equalise. That situation cannot go on.
"I am sure that Slaven, his backroom staff and the team were not happy with what happened and they will think about it a lot over the next few days."
Bournemouth's win was all the more remarkable given they missed two penalties, with King firing wide before Benik Afobe's weak effort was saved by Darren Randolph.
"Obviously, I was annoyed that I missed the penalty, but it was early in the game and as a striker you need to keep your head cool and I knew there would be more chances in the game - luckily I got three more," King told the Bournemouth website.
"It was good character to come back and win the game after missing the two penalties.
"We're a team and we're backing each other. I didn't see anyone pulling faces when we missed the penalties. I knew I had my team-mates behind me so that was the most important thing.
"It's amazing for the club as well, we've been struggling a bit in 2017 and leaving with three points was a good feeling."