A second-half howler from Jamie Ashdown condemned Pompey to a 2-0 defeat at QPR.
Adel Taarabt’s spilled strike and Clint Hill’s header were the difference between the Blues and the Championship leaders.
Pompey delivered a fine performance for an hour against Neil Warnock’s men.
But they were undone as a speculative effort from Taarabt just before the hour mark was spilled by Ashdown and trickled in.
Hill’s header from Taarabt’s header finished Pompey off with 17 minutes remaining.
Pompey had a number of chances themselves, with Greg Halford having a free header after 30 seconds which he failed to direct past Paddy Kenny.
A blockbuster of a free-kick from Halford was then superbly saved by the QPR keeper after 35 minutes.
Steve Cotterill’s side continued to push throughout the second half, with Jonathan Hogg, David Nugent and substitute Nadir Cifci all failing to convert opportunities.
That meant the Blues remain on 31 points from 28 games - four points off the bottom three.