Patrik Berger lightened the Christmas gloom of manager Harry Redknapp with two second-half free-kicks.
Redknapp, who cancelled Christmas leave to intensify training, even managed a smile at the final whistle as Portsmouth jumped out the bottom three.
They had lost nine of their previous 12 Premiership matches, but for Tottenham the alarm bells rang after a poor display in rain and a howling wind.
David Pleat's team suffered their third successive defeat and face a grim battle of their own in the New Year to avoid distress in May on this showing.
Tottenham held the edge in the first half and Robbie Keane should have done better in the 41st minute than drill a shot against the legs of Dutch stand-in goalkeeper Harald Wapenaar.
Keane also cleared a header from Arjan De Zeeuw from the line while the busy Yakubu Ayegbeni could only shoot over the bar from six yards at full stretch.
Russian captain Alexei Smertin saw a tremendous shot from 30 yards tipped over the bar by Kasey Keller.
Berger's goals came after the break soon after a shot from the same player had drifted narrowly wide.
In the 52nd minute Berger smashed a free-kick from almost 35 yards goalwards with his left foot and Keller was slow to react as the ball flashed past him into the corner.
Berger's second came 16 minutes later after Ayegbeni had been brought down on the edge of the area.
This time Berger's free-kick was aimed straight at the Spurs' wall, but with the aid of a deflection Keller this time stood no chance.
Former Tottenham players Teddy Sheringham and Tim Sherwood both contributed fully to the downfall of their ex-club, but Sherwood did not see the match out.
After 77 minutes he was taken from the field on a stretcher after a collision with Argentinian full-back Mauricio Taricco and was replaced by Richard Hughes.