Tottenham dominated large parts of the game but were lacking in creativity whereas United, when given the opportunities, were simply devastating.
Spurs thought they had taken the lead when Louis Saha's shot flew in off Emmanuel Adebayor but referee Martin Atkinson ruled it out for a handball and from then on, the visitors put the home side to the sword with a display that showed exactly why they are firmly in the hunt for their 20th league title.
Wayne Rooney rose to nod home a Young corner on the stroke of half-time and the former Aston Villa man then went on to add two in the second half - the first an acrobatic scissor kick, and the second a superb curling effort from 30 yards.
Jermain Defoe pulled a goal back three minutes from time but it was too little, too late, with Spurs now 13 points behind City and surely out of the Premier League title race once and for all.
The defeat - their first at home since Manchester City thumped them 5-1 in August - leaves them only four points ahead of Arsenal ahead of a tough run of fixtures.
This fixture has brought about many classics in the past, but this game started off slowly on a soggy afternoon in north London.
The absence of the suspended Scott Parker, injury victim Rafael van der Vaart and the ill Gareth Bale hit Spurs, although Sandro and youngster Jake Livermore did their best to deal with the imposing United midfield.
The visitors dominated the opening 15 minutes with Paul Scholes giving a master class in dictating the play in the middle of the park.
The Red Devils failed to fathom any chances, though, and Spurs soon started to take a grip on proceedings.
Aaron Lennon, recalled to the starting line-up after missing the past six games, rushed forward after cutting in from the flank before Jonny Evans put in a crucial block.
David De Gea then nervously palmed away a shot from Adebayor, who burst forward after picking up Sandro's pass.
The crowd sensed a goal and Lennon continued to cause havoc down the right, whipping over a ball that ricocheted about the box. Tottenham suspected the ball had hit a United hand but Atkinson shook his head.
Younes Kaboul then fired a bullet of a free-kick that went just wide before Rooney ventured forward only at the other end only to be cut out by Ledley King.
Spurs poured forward looking for an opener and they thought they had it in the bag in the 38th minute.
Lennon snuck in to the box and Saha turned his cross straight at Adebayor, who backheeled the ball into the net. However, he controlled the ball with his arm, albeit it appeared unintentionally, and Atkinson disallowed the goal.
The home contingent in the sell-out crowd vented their fury at the referee and their despair deepened on the stroke of half-time as United took the lead.
Sandro saw yellow for a late tackle on Young and the resulting free-kick saw Spurs concede a corner which Young swung in for Rooney to head home with Brad Friedel well beaten.
Spurs came out for the second half fired up, Livermore stinging De Gea's palms with a fierce drive before Kaboul headed narrowly wide.
Benoit Assou-Ekotto skimmed the top of the bar with a wicked curling free-kick as Tottenham upped the pressure but the home crowd were stunned in to silence on the hour as United added a second.
The Spurs defence switched off at a throw-in, allowing Nani to skip in to the box and fire a cross that ricocheted in to the path of Young, who adjusted his body to fire in a fine scissor kick.
Ferguson immediately brought on Ryan Giggs for Scholes and the travelling supporters mocked the home side by chanting "Harry for England".
United were starting to play some sublime football and their third came in the 68th minute in spectacular style.
Tottenham's defence backed off Young and he made them pay by unleashing a brilliant 30-yard strike that flew in over an outstretched Friedel.
More taunts came from the away fans as United threatened to go on the rampage.
Harry Redknapp brought on Niko Kranjcar, Danny Rose and Defoe to freshen things up and the move paid dividends to a minor extent when Defoe pulled back a consolation.
The former West Ham man picked up a wayward ball and advanced towards the United back line before belting home a 25-yard drive.
Spurs continued to push forward but two more goals in the three added minutes was too tall an order and United walked away with all three points.