In a game littered with errors which fell well short of the classic many had predicted, the Red Devils called on all their experience to keep their nerve and win.
The first half had been so bad that the game had all the ingredients of an end-of-season affair with nothing at stake.
Both teams seemed to wake up to the fact that there is a league title to be won and a Champions League place at stake in the second period.
United broke the deadlock in the 58th minute. Former Spurs striker Dimitar Berbatov, who had replaced Wayne Rooney - out with a groin strain - produced a mazy run into the Tottenham box.
His clever flick to his left found full-back Patrice Evra and he was tripped as he skipped past Benoit Assou-Ekotto.
Referee Andre Marriner pointed to the spot and although goalkeeper Heurelho Gomes guessed right, Giggs' left-foot penalty carried too much power and accuracy as it flew past him and into the bottom right corner of the net.
Spurs bounced back to equalise in the 70th minute.
Gareth Bale's corner into the centre of the United box saw Tottenham skipper Ledley King rise above Jonny Evans to place his firm header into the bottom left corner of the net from seven yards.
United looked flat but they were reinvigorated with nine minutes to go thanks to the best goal of the game.
Darren Fletcher found Federico Macheda 25 yards out and he slipped the ball forward to Nani, who skipped past King before scoring with a superb right-foot chip over Gomes and into the corner of the net from 12 yards.
Another touch of Nani magic set up United's third goal four minutes later.
The Portuguese winger's superb run into the Spurs box ended when he was brought down by Wilson Palacios.
Mr Marriner again pointed to the spot and Giggs changed his routine when he fired his left-foot shot into the bottom left corner of the net beyond the diving Gomes' despairing dive.