Jason Roberts celebrates scoring Blackburn's second goal
Derby will finish the season with the lowest number of points in Premier League history after Blackburn came from behind to earn a comfortable win.
Kenny Miller gave Derby the lead when he controlled Roy Carroll's long pass to finish beyond Brad Friedel.
But Roque Santa Cruz levelled after Carroll failed to deal with Morten Gamst Pedersen's long-range effort.
Bad defending led to Jason Roberts's second-half goal while Santa Cruz's header secured the win for Rovers.
Victory over Derby and Wigan's 2-0 win over Aston Villa ensures Rovers keep alive their slim hopes of qualifying for Europe via the Intertoto Cup.
But the Rams' defeat rubber-stamped their season as the worst since the league's formation.
With one game remaining they are still four points adrift of Sunderland's tally of 15 in the 2005/06 season, and they need to score against Reading next week to avoid becoming the Premier League's lowest scorers.
Hughes hopes a big investor will help his side improve
Despite their team's sometimes woeful performances this season the visiting fans were intent on enjoying the penultimate game of the season.
Right from the kick-off Derby's supporters, many in fancy dress, sang "we're going down but we're having a laugh" and there was a certain joie de vivre in the way their team played in the first half.
Derby deservedly took the lead in the 19th minute when the lively Miller coolly shot low past Friedel's right.
Blackburn were not without their chances, however. Roberts was guilty of dawdling inside the box when he should have opted for power, while David Bentley was inches from beating the back-peddling Carroll with a delightful chip.
Derby have only managed to keep three clean sheets all season so it was no surprise when Cruz side-footed in from close range for his 22nd goal of the season, even though the visitors deserved to go into the break ahead.
Derby manager Paul Jewell had accused his defence of "comic book" defending after Monday's 6-2 defeat to Arsenal, but the back-four antics which led to Rovers' second goal a minute into the second half was more slapstick.
Andy Todd failed to deal with a long ball and a grateful Roberts latched onto the defender's misplaced pass and found the left corner of goal.
It was all Rovers from then and Roberts had a host of chances to extend his side's lead.
Jewell praised his team's 'Premier League' fans
Carroll's fingertips prevented the striker's acrobatic overhead kick from sneaking into the top corner and a few minutes later the Northern Ireland goalkeeper had to be alert to tip another effort away for an innocuous corner.
The former Wigan striker's worse miss came on the hour when, with just Carroll to beat, he lingered for too long and allowed the goalkeeper to save with his feet.
But Roberts's profligacy mattered little in the end as, with 13 minutes remaining, Cruz headed a menacing David Bentley cross for his second of the match.
Blackburn manager Mark Hughes:
"We've never been out of the top 10 all season and for a club of our size that is a huge achievement.
"Derby pegged us back in the first half and worked extremely hard to get themselves in front.
"We came out for the second half with a lot more drive and purpose and were comfortable winners."
Derby manager Paul Jewell:
"It would have been nice to have got six points from our last two games but it wasn't going to happen.
"The important thing now is trying to build for next season. There has to be a whole culture change.
"We've to be mentally stronger and physically stronger. We played well for 44 minutes but didn't concentrate."
Blackburn: Friedel, Reid, Samba, Nelsen, Warnock, Bentley, Emerton, Vogel (Kerimoglu 61), Pedersen (Olsson 79), Santa Cruz, Roberts (Derbyshire 79).
Subs Not Used: Brown, Ooijer.
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