Pompey were held to a 0-0 draw by Leeds at Fratton Park.
But the Blues will feel a blatant first-half penalty not being given cost them the chance of three precious survival points.
Darren O’Dea’s clear handball in the box was not given by referee Phil Gibbs.
That was crucial, but the good news was Peterborough’s late equaliser against Doncaster kept Pompey off the bottom of the table.
There were plenty of chances for Pompey, with Hayden Mullins twice going close in the first half.
Joel Ward had a couple of headers which were saved by Andy Lonergan.
Both teams had the ball in the back of the net in the second half, but Robert Snodgrass was offside as he headed home and Greg Halford’s throw went directly into the net with nobody touching it.
New-boy Scott Allan was lively but went out of the game as the match wore on.
The result leaves Pompey one off the bottom of the table on 26 points.
But they are now five points from safety with 14 games to go.