The club's 3-1 reversal to the Essex side on Tuesday evening was their fourth defeat in their last five matches.
"That was disgusting. I'm absolutely embarrassed. It's not acceptable," Robinson told BBC Three Counties Radio.
"[No] hunger, fight, determination. A lack of understanding. Stupid mistakes and getting punished. Shambolic. Absolutely rubbish.
"That's as embarrassed as I've ever been on a touchline. First half we did OK. But other than that there wasn't a positive. I've got a job on my hands. It's the lowest and most difficult it's been for me and I have to respond in the right way."
Robinson's side occupy 12th place in the table following the defeat.