Shabani Nonda scored two goals and missed a penalty as Blackburn dented Pompey's Uefa Cup qualifying hopes.
Nonda has now scored seven league goals this season
Nonda volleyed Blackburn into the lead after just 57 seconds when he latched on to Sol Campbell's weak back header.
The Blackburn striker capitalised on more poor defending for his second when he prodded home after a mix-up between David James and right-back Noe Pamarot.
Nonda crossed for Stephen Warnock for Blackburn's third, though James saved the former Roma striker's penalty.
606 DEBATE: Give your thoughts on the match
After a bright start to the league campaign Portsmouth are finding it tricky to emerge from a poor spell that has seen them pick up just five points in their last eight games.
The visitors might have given Blackburn more than a helping hand with the first two goals, but Warnock's strike illustrated the quiet progress Rovers are making under Mark Hughes.
The former Liverpool defender started and finished the move to score his first Blackburn goal as Rovers broke from one end of the pitch to the other in devastating fashion.
The game also afforded Tugay an opportunity to provide one of his midfield masterclasses.
The 36-year-old Turk is not one for doing much running these days, but he compensates with an almost effortless ability to bring his team-mates into play.
Catch him while you still can.
Portsmouth boss Harry Redknapp threw Kanu and Niko Kranjcar at the start of the second half but the double substitution had little impact.
Indeed Portsmouth continued to make life difficult for themselves, with James again the culprit, needlessly conceding a penalty after fouling Morten Gamst Pedersen.
James partly redeemed a less than distinguished performance by saving Nonda's penalty as the Blackburn striker missed the chance to claim his first hat-trick in English football.
Portsmouth found themselves chasing the game inside the first minute.
Campbell was caught out by the flight of a David Bentley cross and was only able to head the ball backwards.
Nonda pounced on Campbell's mistake, beating James with a clipped volley from an acute angle.
So sluggish were the visitors that Pompey's manager Harry Redknapp was soon on the touchline urging more effort from his side.
But his words of encouragement had little effect as more comedy defending allowed Blackburn to extend their lead.
When Matt Derbyshire crossed from the right James and Pamarot got in the way of each other allowing the ball to reach Nonda who slotted the ball in with his left foot.
Portsmouth were fortunate not to concede a penalty in that error-strewn opening period when Portsmouth defender Linvoy Primus pushed Derbyshire in the box after Pedersen crossed from the right.
Indeed Portsmouth were lucky to only concede three goals, given the number of chances Blackburn continued to create, with Nonda and David Dunn passing up reasonable opportunities.
Blackburn manager Mark Hughes:
"We feel we can have a real go at getting that sixth place for European qualification.
"I just sense we'll be in the mix come the end of the season and I was really encouraged by this display.
"Our performance was excellent and we were on the front foot from the very first minute."
Portsmouth coach Joe Jordan:
"Our form away from home hasn't been good enough.
"It was very disappointing. The performance was awful. We were looking to get back into sixth but we started poorly and things didn't get better.
"That is as poorly as we have played all season. We have to learn from this and put it right."
Blackburn: Friedel, Emerton, Samba (Khizanishvili 46), Henchoz, Warnock, Bentley, Mokoena, Kerimoglu, Pedersen (Dunn 75), Nonda, Derbyshire (Roberts 54).
Subs Not Used: Brown, McCarthy.
Booked: Derbyshire, Pedersen.
Goals: Nonda 1, 25, Warnock 50.
Portsmouth: James, Johnson, Primus, Campbell, Pamarot (Kranjcar 46), O'Neil, Davis (Kanu 46), Pedro Mendes (Mvuemba 55), Taylor, Cole, LuaLua.
Subs Not Used: Ashdown, Traore.
Booked: Taylor, Davis, Mvuemba.
Ref: M Clattenburg (Co Durham).