The Clarets' survival fight suffered a major set-back as they gifted crisis club Portsmouth a rare win to stay in lodged in the bottom three.
Burnley boss Brian Laws had insisted this was not a must-win game - and the mathematics prove him right with the Clarets still in touch with a clutch of clubs just above them.
But Laws' men have to start winning soon and this was an opportunity that passed them by against the bottom club, which arrived at Turf Moor facing almost certain relegation thanks to the nine-point penalty they will incur for going into administration.
Rather than deflate them, though, that seemed to allow Pompey to play with a freedom that Burnley struggled to embrace, despite a superb equaliser from Martin Paterson.
Paterson had cancelled out Frederic Piquionne's opener before half-time with a sublime finish - and even through Brian Jensen then saved a penalty from Jamie O'Hara the Clarets could not hang onto the consolation of a potentially useful point.
Clarke Carlisle conceded another spot-kick with 14 minutes to go and this time Hassan Yebda's conversion put another chink in Burnley's proud Turf Moor record.
Once again Laws had shown that he is not afraid to make changes as he brought back Robbie Blake and Wade Elliott and gave Paterson a first start since September in place of the ineligible David Nugent.
Get in ! Martin Paterson makes it 1-1
But as if the weight of expectation was sitting heavily on their shoulders, the Clarets made an uncertain start.
Portsmouth played with a spirit that belied their off-the-field problems and had the ball in the net after 14 minutes but Danny Webber's effort was ruled out as his touch, following a short corner, came from an off-side position.
Paterson and Fletcher did their best to ruffle a few feathers at the other end but Pompey took the lead after 25 minutes when Webber made space for a low cross-shot which Piquionne turned in at the far post.
Burnley needed a response and Blake and Fletcher looked to provide as they engineered a break which ended with Fletcher shooting over and Kevin McDonald forcing David James to scramble the ball away for a corner following a driving run into the penalty area.
And the goal the Clarets desperately needed came after half-an-hour thanks to a touch of class from Paterson.
The Northern Ireland international had looked typically full of running and also showed his finishing is rust-free following his lengthy lay-off as he netted for the same game running.
Martin Paterson shows his delight at levelling
Fletcher again did well as he challenged for Jensen's long kick and as the ball skimmed off the top of his head Paterson pounced to engineer a clever lob over James with the outside of his right boot to make it 1-1.
That should have lifted the pressure but with nothing to lose Portsmouth kept going forward and five minutes before the break almost regained their lead.
O'Hara was frequently given too much space in midfield and when he picked up a pass from John Utaka he clipped a shot against the underside of the bar from 20 yards.
The rebound dropped nicely for Webber but his goalbound shot was well blocked by the recovering Fox.
Burnley were living dangerously and ten minutes into the second half they engineered another escape thanks to the brilliance of Jensen.
Carlisle's rash challenge on Piquionne gave away a penalty but spot-kick king Jensen, who had also saved from 12 yards at Fratton Park, came to the rescue again as he went to his left to block O'Hara's effort.
Brian Jensen saves the Clarets once
The Clarets looked to capitalise and overcome the understandable tension around Turf Moor and with an hour ticking past they should have gone in front.
Paterson had stretched the Pompey defence all afternoon and he did it again to deliver a fantastic cross from the right which Fletcher headed over from in front of goal six yards out.
Laws sent on Chris Eagles and Jack Cork in a bid to maintain the momentum as Burnley began to take a grip and search for a winner and Fox went close with a long range effort which skidded just wide.
But instead of going for three points the Clarets were suddenly looking at none as they gifted Portsmouth a second goal with 15 minutes to go.
Carlisle was again the culprit as he got caught in possession from a Fox throw and then tripped Utaka to concede another penalty.
This time Yebda took on the responsibility and beat Jensen to give Portsmouth only their second away win in 27 attempts in the Premier League as they survived with ten men in the dying stages following the dismissal of Ricardo Rocha for a second bookable offence as the Clarets piled on the pressure without success.
The 'Beast' can't repeat his heroics as Yebda scores
Burnley: Jensen, Mears, Fox, Carlisle, Cort, Elliott (Eagles 63), McDonald, Bikey (Cork 63), Blake (Thompson 79), Fletcher, Paterson. Substitutes: Jordan, Edgar, Duff, Weaver.
Portsmouth: James, Finnan, Wilson, Hreidarsson, Rocha, Belhadj, O'Hara (Brown 90), Yebda, Webber (Diop 90), Piquionne, Owusu-Abeyie (Utaka 39). Substitutes: Mullins, Kanu, Dindane, Ashdown.
Referee: Mark Clattenburg