Blackpool, who started the match just two points clear of the relegation zone, succeeded where AC Milan failed last week with goals from Charlie Adam, DJ Campbell and Brett Ormerod.
Spurs, who beat Milan 1-0 at the San Siro in their Champions League last 16, first leg tie after climbing to fourth in the Premier League on the back of three straight wins, got a late consolation goal from Roman Pavlyuchenko.
Fourth-placed Tottenham stay on 47 points from 27 games and remain two behind Manchester City and two ahead of Chelsea but have now played a game more than the west London side in the race for a top-four finish and Champions League qualifying spot.
Spurs had 25 goal attempts, shots cleared off the line and penalty appeals turned down but the pluck and spirit Blackpool have shown throughout their first season in the top flight for 39 years saw them triumph and move up to 12th spot.
"I've never seen a team miss so many open goals in my life since I've been in football," Tottenham manager Harry Redknapp said of his misfiring players.
"You've got chances from four yards out, three yards out, six yards out and you can't score and (you're) hitting people on the line. It's unbelievable really," he told Sky Sports.
Adam, the target of a Spurs approach in the transfer window, put Blackpool ahead with a penalty in the 18th minute after Sebastien Bassong barged over Campbell, who himself ended a swift counter-attack with their second just before halftime.
Ormerod then wrapped up the victory with his first Premier League goal for seven years 10 minutes from time to complete a record of scoring for Blackpool in all four league divisions.
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