Portsmouth made it five cleansheet wins on the bounce against struggling Scunthorpe thanks to second-half strikes from Dave Kitson and Aaron Mokoena.
But Iron manager Ian Barraclough left Fratton Park fuming after the referee disallowed Lee Miller's first-half header for a seemingly innocuous push.
Pompey were made to work hard for the three points and the breakthrough didn't come until 62 minutes when Kitson showed quick feet before driving his shot past Josh Lillis.
Mokoena added a long-range second with 10 minutes left. Steve Cotterill's side have now gone 506 minutes without conceding a goal in the Championship and a play-off place is not out of reach.
Cotterill said: 'It was a great finish from Kitson and I'm really pleased for him. We're not far from the play-offs now.'
Ian Baraclough - who's side remain four points from safety - raged: 'We should have gone in at half-time 1-0 up. There was nothing wrong with the goal but the referee won't look at the replays.'
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