Pompey slumped to 16th in League Two following a third successive defeat.
Promotion-chasing Bury were the latest to inflict a loss of the Blues with a 1-0 victory at Fratton Park this afternoon.
Substitute Ryan Lowe’s 45th-minute free header from six yards out separated the sides in a largely lacklustre affair.
As a result, Gary Waddock has still to pick up a point or a goal following two matches in charge as caretaker boss.
Keeper Nick Pope did tip over a Jed Wallace shot from inside the penalty area during the first half, but that was largely it from the disappointing Blues.
The hosts were not dominated by Bury, yet once David Flitcroft’s side took the lead they never looked like surrendering it.
Injury-hit Pompey, with just six players on the bench, did give a full league debut to Ben Close, while Academy midfielder Adam May made an entrance off the bench for his bow.
Yet, overall, Waddock’s men struggled for creativity throughout, ensuring it was a far too comfortable afternoon for the Shakers.
Now it’s all eyes on the manager hunt as Pompey’s board seek to address this dreadful season.