Bent beat Magpies' goalkeeper Harper at the second time of asking
Newcastle's hopes of staying in the Premier League took a huge blow after being easily pushed aside by Tottenham.
Seconds after a Kevin Nolan effort, Spurs broke away and Darren Bent curled in a first-half opener after Steve Harper had parried away his first shot.
Tom Huddlestone impressed with long-range shots, while a Jonathan Woodgate header was tipped over by Harper.
Newcastle improved in the second half and substitute Obafemi Martins volleyed agonisingly over in the dying minutes.
The struggling visitors scored a dramatic late equaliser at Stoke last week but Martins spurned the chance to ease the Magpies' relegation worries at White Hart Lane.
They remain four points from safety, and with manager Alan Shearer claiming before the match that they could not afford to lose any more games, he opted for three central defenders and Damien Duff employed as a wing-back.
Europe would be a bonus - Redknapp
It was a cautious approach and his players looked edgy in possession, as Tottenham in contrast looked bright and full of creation and Bent could have had a hat-trick within the opening 20 minutes.
With Huddlestone's fine passing dictating proceedings, it was of little surprise that Spurs took the lead, although it arrived after Newcastle's best chance of the first half.
Heurelho Gomes smothered Kevin Nolan's tame shot and Spurs quickly poured forward on the counter.
Modric tried to pick out Keane with an incisive pass but, Sebastien Bassong's sliding challenge inadvertently supplied the assist to Bent on the left.
The Englishman's low shot was well saved by Harper, but the striker was lucky enough to pick up the rebound and he made no mistake with a curling shot to grab his 16th goal of the season.
Spurs deserved their lead and came within a Harper knuckle of doubling the advantage with the Newcastle keeper tipping over a 20-yard piledriver from Huddlestone.
With Michael Dawson stretchered off after falling heavily from a header, the visitors may have sensed an opportunity to expose the Tottenham back line. But substitute Alan Hutton immediately impressed and almost created a second goal.
The Scottish defender burst forward in the final minute of the first period and picked out Bent at the back post, who could only head high over the bar.
The second half continued in similar fashion and Wilson Palacios - returning after his ban - had a fine chance on the hour but his shot was blocked brilliantly by the impressive Bassong.
Newcastle needed a change desperately and with 25 minutes remaining Martins and Mark Viduka were introduced up front in place of Andy Carroll and Nolan.
Fight for places gives us the edge - Bent
The lively pair made an immediate impact with Martins blazing over from 18 yards and he then wasted a header from six yards out.
The Nigerian had the ball in the back of the net after a drilled shot on the edge of the box but it was disallowed for what appeared to be a harsh handball decision.
With Spurs starting to give possession away, Jermain Defoe - having recovered from a broken foot - was introduced to liven up the home side's play.
With 10 minutes remaining, a Woodgate header from Modric's corner was brilliantly tipped over but Newcastle dug deep and fought back, albeit in spurts.
Home wins are essential now - Shearer
With two minutes left it was Martins again making a menace of himself and he controlled the ball with his chest before volleying over from three yards out.
It was their final chance of the game and after 16 years in the Premier League, Newcastle and Alan Shearer head into their final five matches with the threat of relegation hanging heavily upon them.
Tottenham boss Harry Redknapp:
"It was a good win and another clean sheet. We had opportunities to score more but I was pleased - our defensive record is incredible.
"You win 1-0 and that's what good teams do."
Newcastle manager Alan Shearer:
"The one positive is the second half - we did a lot better.
"We had to start with three at the back. It worked against Stoke (when Newcastle drew 1-1) but we struggled in the first half today."
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