Liam Lawrence missed a penalty with the very last kick of the game which meant Brighton took all three points at Fratton Park following another poor performance at home.
It was a very frustrating game to watch courtesy of low quality football, niggly fouls and a fussy referee who seemed to get many decisions wrong on the day.
That's not to say that we should be blaming the referee for this defeat as Pompey failed to create many clear cut chances, struggled to break down a stubborn Brighton back line and couldn't pass the ball accurately.
A goalmouth scramble and a deflected effort that Marcos Painter cleared off the line was the closest Pompey came to scoring as Steve Cotterill's men edged a poor first half but it was Brighton who took the lead in first half stoppage time.
The visitors were allowed to get numbers forward and Craig Noone's low cross was touched by Craig Mackail-Smith and the ball trickled into the bottom corner of the net.
Steve Cotterill must have said some harsh words (again) at half time as Luke Varney was presented with the perfect chance to equalise as Joel Ward's cross found him in space in the box but the striker could only blaze over the bar when he should have scored.
The only other chance for Pompey in normal time came when substitute Dave Kitson came agonisingly close to getting his head on Lawrence's cross.
Ashdown was being kept busy at the other end, having to be alert to tip Noone's effort around the post but the second half was mainly filled with fouls and bookings for dissent.
However, it seemed like Pompey would get out of jail in stoppage time again when Lewis Dunk tipped Lawrence's cross into the box away with his hand.
However, there would be agony for the home fans as the Irishman's spot kick crashed off the post and Kasper Ankergren gathered Tal Ben-Haim's follow up to end what was a miserable day at Fratton Park.
It's only two weeks into the new season and already we're starting to see the ugly side to Steve Cotterill's team. Unattractive hoofball in desperate search of an equaliser and bookings for petty fouls and dissent.
If we had got a point yesterday it would have been hard to justify it after a performance littered with poor passing and very little creativity. If the owners were watching, they'll know that more signings, such as the surprise return of Benjani, are required if we want to avoid a relegation battle.
Reading come to Fratton Park on Tuesday which is arguably going to be tougher than yesterday's game. So Pompey need to buck their ideas up quickly.
Pompey Player Ratings
Jamie Ashdown: 6 - Solid showing.
Tal Ben-Haim: 6 - Did OK.
Greg Halford: 5 - Could have done better.
Aaron Mokoena: 7 - Was our best performer, which says everything really.
Hermann Hreidarsson: 6 - One of our bigger threats going forward, which again highlights our problems.
Liam Lawrence: 4 - Missed crucial penalty.
Joel Ward: 4 - Well below par.
David Norris: 5 - Didn't get into the game.
Hayden Mullins: 4 - Lost the midfield battle.
Luke Varney: 4 - Missed a great chance and can't beat a man.
Kanu: 5 - Predictably faded as the game went on.
Substitutes
Stephen Henderson
Ricardo Rocha
Christian Dailly
Ryan Williams (Hreidarsson 83): N/A - Should have been given more time.
Dave Kitson (Ward 68): N/A - As much as he is criticised, he should have started ahead of Kanu.