Andy Robinson's goal from the edge of the box in first-half injury-time gave Tranmere a 1-0 win at Greenhous Meadow.
"We had a lot of the ball for the first 35-40 minutes and I thought we got it into good areas without producing the final pass or cross that would have caused them problems," said Turner.
"What we did, which was criminal, was to concede the goal just before half time.
"Tranmere clearly had a game plan. They came and defended in depth, were quite happy to clear their lines for the first 40 minutes, and we kept coming back at them, but you can't concede the goal in the manner which we've done.
"That just put everybody on edge. You could see the confidence drain a little bit from players on the back of two previous defeats here.
"It's a time now for us to batten down the hatches, to stay together and to work that much harder."
Turner, whose side remain four points above the relegation zone, now wants a positive response at home to Preston on Sunday.
He added: "All we can do is prepare for the next one and try and keep the players' confidence as high as possible."