Havant slipped back into the London one south danger-zone with a disappointing 29-14 defeat at fellow strugglers Hove.
The visitors failed to adapt to the wet and muddy conditions and lacked the necessary intensity.
‘It was a very poor performance in dire conditions,’ said head coach Will Knight.
‘We lacked the intensity and organisation to cause them many problems.
‘They controlled the game, pinned us back and took their opportunities from broken play.’
The visitors started poorly and Hove scored a converted try within seconds of the start.
Havant hit back when Grant Morris fed Nick Goodger to score and Joel Knight added the conversion to level the scores at 7-7.
Two home tries in the space of five minutes, however, put the visitors on the back foot.
Winger Josh Blackburn finished well to put Havant back in the game.
But just before the interval, poor tackling enabled Hove to go in at the break with a 26-14 lead.
Though Havant had a good share of the possession in the second half the only score resulted from a Hove penalty.
Portsmouth remain rooted to the bottom of London Two south west following their 13-11 local derby defeat at Winchester.
‘It was disappointing because if we had switched on a bit earlier in the first half things would have been very different,’ said director of rugby Ed Neville.
‘Our forwards were off the pace in the opening forty minutes and failed to compete at the breakdowns.
‘In the second half we were rarely out of the Winchester half and spent most of it inside their twenty-two.
‘That showed what we are really capable of and that we can more than compete at this level.
‘But at the end of the day it is another defeat.’
Dan Neville scored two penalties for Portsmouth.
In the final minute Adam Long forced his way over in the corner to give the visitors a lifeline but the touchline conversion proved just too difficult for Neville.
In Hampshire two Southsea Nomads lost 27-14 at home to Chineham.