Liam Lawrence blasted Pompey's defending after watching Hull steal three points.
Nigel Pearson's side ran out unlikely 3-2 winners in a match the Blues dominated.
The scoreline was harsh on Steve Cotterill's men, who failed to capitalise on more than 20 goal-scoring opportunities.
Instead, Hull snatched the victory with two goals in three second-half minutes.
That's nine goals shipped during the past three games by the Blues defence, following a 3-3 draw at Leeds and a 3-0 defeat at Watford.
Lawrence netted a penalty and provided the corner for Greg Halford's goal in the moments the hosts did manage to net.
But afterwards he was furious at the defending which gifted the Tigers their triumph.
He said: 'I thought we were brilliant at times.
'We played some great stuff but we didn't defend. That's it.
'They must have had three chances and scored three goals.
'We've had nine or 10 good chances and scored two.
'We keep saying you can't score goals every game and we have the sort of side which will create chances.
'But we just need to make sure at the other end we don't give anything away. If we can address this I am sure we will be alright.
'The papers today will have said about this, that and the other, but if you'd gone to the game you would know the truth.
'My mate, their captain (Ian Ashbee), went home absolutely buzzing with the result because he knows to come here the way we played and to beat us was an unbelievable result.
'We didn't defend and maybe we should have scored another goal but you shouldn't need to score three goals at home to win a game.
'We weren't good enough defensively.'
Pompey have now conceded 37 goals in 24 league games this season.
They have also racked up just three clean sheets, the only home shut-out coming against Ipswich back on September 11.
Clearly it's a major headache for Cotterill as he looks to tighten up his defence.
However, matters weren't helped with Ricardo Rocha limping off with what appeared to be a hamstring problem, leaving him a major doubt for the FA Cup clash with Brighton this weekend.
Greg Halford could also be suspended if he fails in his appeal against his Watford sending off.
The Wolves man also believes defeat yesterday was an unfair result.
Halford added: 'I had a penalty given against me and it wasn't even a tackle. I stood my ground.
'I've seen the replay and, if anything, I've taken a step away from him (Cameron Stewart).
'He jumped in the air and made a meal of it but we created plenty of chances, we just didn't take them.
'It could have been five or six to us, we just need to be more clinical.'