Paul Collingwood admitted England's batsmen had made some poor choices as they were bowled out for just 160 chasing 183 to win the third one-day international on Saturday.
"In terms of decision-making we weren't quite there with our batting," he said.
"The effort was certainly there all day and I'm not going to blame the bowlers who were fantastic, but as a batting unit we should have got 180-odd."
"It was very disappointing; we were in a position to be pretty ruthless and go 2-0 up but things didn't go our way."
England enjoyed several moments of supremacy on a chilly day in Bristol, reducing New Zealand to 75-6 at one point, and starting their chase well when they were 62-2 early on.
But whereas New Zealand had lacked the killer punch in the Test series, this time it was the home team who let the opposition back into the match.
Collingwood maintained a positive outlook for the last two matches in the series, but his team now have to triumph in both to win it.
He said: "The batsmen seemed to edge a few or hit them straight to fielders, but we've played some good cricket so far in the series and will hopefully win the next one."
An ecstatic New Zealand captain, Daniel Vettori, said: "It keeps us in the series and we go to London with a lot of confidence.
"To defend 180 today was an outstanding effort. After the situation we had been in over the past three weeks it was a fantastic feeling for us."
He said 19-year-old Tim Southee, pipped to the man-of-the-match prize by Kyle Mills, deserved a huge amount of credit.
"The wicket had quite a bit in it. It was almost three-paced, with ones that went quicker and ones that went slower.
"Tim's first three overs were a struggle, but to come back and take 4-38 was outstanding.
"Grant Elliott had a great performance so there were one or two unexpected performances, but ones we are cherishing.
"Hopefully the momentum is with us at the moment and hopefully we can carry it through."