Leeds, going well in the third tier of English football, had knocked out Manchester United at Old Trafford in the previous round and snatched a 2-2 White Hart Lane draw in the original game.
But the run of upsets that have been a feature of the competition so far this season came to an end as the full-strength Londoners dominated from the start, weathered a brief Leeds comeback before deservedly advancing to an away tie with Bolton Wanderers on the weekend of February 13/14.
Spurs flew out of the blocks but Defoe, via a combination of poor finishing and good goalkeeping by Casper Ankergren, wasted half a dozen chances.
The England striker finally found the target after 37 minutes when he collected a low David Bentley cross, spun and completely miskicked a half-volley that looped beyond Ankergren.
The goal spurred Leeds into their most impressive spell of the game and in stoppage time they equalised when Jermaine Beckford's hooked volley was parried by Heurelho Gomes with Luciano Becchio on hand to slide in the rebound.
Spurs continued to make most of the running in a high-octane second half but Ankergren made several more good saves and when he was beaten again by Defoe after 68 minutes the goal was ruled out for offside.
Five minutes later though Defoe was on hand again to turn in a fizzing cross from the impressive Bentley.
Unlike in the last game, when Beckford equalised with a stoppage-time penalty, Spurs kept their cool, and as Leeds threw everything forward at the death Defoe broke clear to tuck in his third of the night and 20th of the season.
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