England winger Young scored twice in nine minutes at White Hart Lane after Wayne Rooney's 44th-minute header had given United a fortunate half-time lead against third-placed Spurs who worked tirelessly throughout the game but lacked a cutting edge.
Substitute Jermain Defoe scored a late consolation for Tottenham who suffered their second convincing defeat in eight days after last week's 5-2 thrashing at North London rivals Arsenal
With 11 games remaining champions United have 64 points to the 66 of City with Tottenham on 53, four ahead of Arsenal in the race for an automatic Champions League spot.
"We had a bit of luck," United manager Sir Alex Ferguson, taking charge of his 986th league game to go ahead of the club record he shared with Matt Busby, told Sky Sports.
"Scoring right on half-time it was probably our first chance at goal. That was a killer for Tottenham because they must have been sitting there wondering how they are losing 1-0."
Chelsea, who sacked manager Andre Villas-Boas on Sunday, are a further three points behind. Tottenham manager Harry Redknapp said the Portuguese's exit would not have any impact on the race for a top-four finish.
"Not unless Jose Mourinho is coming it's not going to effect it and I don't think he's coming this week," he told reporters.
Newcastle United's hopes of challenging for a top-four spot suffered a blow with a 1-1 draw against 10-man Sunderland, Shola Ameobi scoring a stoppage-time leveller for Newcastle.
Sunderland took the lead through Nicklas Bendtner in a bad-tempered north-east derby but the visitors had Stephane Sessegon sent off for an elbow.
Wolverhampton Wanderers slipped into the relegation zone after a 5-0 drubbing at Fulham, for whom Russian Pavel Pogrebnyak scored a hat-trick and Clint Dempsey two.
Ferguson had identified the fixture at White Hart Lane as a massive game in his side's quest to prevent City stealing their title and after taking the points despite not playing well his side now look perfectly placed for the final sprint to the line.
Tottenham, bidding for a first win over United since 2001, were without Welsh winger Gareth Bale, Dutchman Rafael van der Vaart and midfield workhorse Scott Parker but were the better side in the opening period.
Lacklustre United offered virtually no attacking threat and Ferguson's 986th half-time team talk in a league match might have involved his dreaded hair dryer had it not been for Rooney's poacher's goal just before the break.
Young's corner was curled in from the left and Rooney evaded the attention of his marker to stoop and head the ball past a helpless Brad Friedel.
It was harsh on Tottenham who had produced some slick attacking play as they attempted to enliven a muted home crowd on a raw, drizzly afternoon in North London.
Aaron Lennon's pace down the right caused problems and former United striker Louis
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