Dundee United leapfrogged St Johnstone into fourth spot with a win that leaves Dunfermline three points adrift at the foot of the Scottish Premier League.
It took dominant United until Jon Daly's superb shot on the turn after 49 minutes to break the deadlock.
In-form winger Gary Mackay-Steven weaved his way to the bye-line to set up Scott Robertson for a clinical finish with 10 minutes remaining.
Daly fired his second three minutes later to bury the disappointing Pars.
And stretching their unbeaten league run to nine games moves United ahead of the Saints on goal difference before the Perth side head to Celtic Park to take on the Scottish Premier League leaders on Sunday.
For Dunfermline, it was a chance missed to move level with second-bottom Hibernian, who visit Inverness Caledonian Thistle, also on Sunday.
Kevin Rutkiewicz and Andy Kirk came in at the expense of David Graham and Liam Buchanan as Pars manager Jim Jefferies adopted a more conservative line-up in an attempt to subdue in-form United.
But immediately the uncertainty at the heart of the defence that has bedevilled Dunfermline was in evidence as Paul Dixon's fine cross was diverted wide by the diving Daly.
Gavin Gunning was next to step out of the home defence and and he sent a long-range drive fizzing past a post.
Pars goalkeeper Chris Smith, whose nervy displays will lead to the arrival of Spanish goalkeeper Bernardo Dominguez next week, survived a scare when his weak punch landed at Dixon's feet and the full-back's first-time effort sailed through a sea of bodies but just wide.
United right-back Robbie Neilson, who had started in place of the injured Keith Watson, should have opened the scoring when he blazed over from six yards after being picked out superbly by Gary Mackay-Steven.
Dunfermline were on the back foot but could have taken the lead after 32 minutes, but Alex Keddie's header from Joe Cardle's free-kick soared over.
Smith did well to turn wide a powerful, 20-yard drive from Mackay-Steven and the Pars would have been pleased to reach half-time with the scores level.
However, they were behind four minutes into the second half when Daly controlled the ball on his chest before swivelling superbly to give Smith no chance with his powerful drive.
Mackay-Steven sent a drive straight at Smith, Johnny Russell ought to have done better than miss the target with a header and John Rankin curled an effort wide as United established firm control.
It was Mackay-Steven who set up the second goal, weaving past three Dunfermline players before rolling the ball back into the path of Robertson.
A dispirited Dunfermline defence was caught napping soon after when Daly was first to respond to a speculative Russell cross as United eased to sixth successive victory.
Full Time The referee blows for the end of the match.
Substitution Richie Ryan comes on in place of Scott Robertson.
Substitution Willo Flood goes off and Danny Swanson comes on.
Substitution Stuart Armstrong replaces Gary Mackay-Steven.
Inswinging corner taken by Joe Cardle from the left by-line, Gavin Gunning manages to make a clearance.
Johnny Russell provided the assist for the goal.
82:47 Goal scored
Goal - Jon Daly - Dundee U 3 - 0 Dunf'mline A goal is scored by Jon Daly from inside the penalty area to the bottom right corner of the goal. Dundee Utd 3-0 Dunfermline.
Chris Smith takes the free kick.
Substitution Paul Willis on for Gary Mason.
Foul by Jon Daly on Alex Keddie, free kick awarded.
The assist for the goal came from Gary Mackay-Steven.
79:25 Goal scored
Goal - Scott Robertson - Dundee U 2 - 0 Dunf'mline Scott Robertson scores a goal from inside the six-yard box to the top right corner of the goal. Dundee Utd 2-0 Dunfermline.
Outswinging corner taken from the right by-line by Willo Flood.
Substitution Liam Buchanan on for Andy Kirk.
Free kick awarded for an unfair challenge on Willo Flood by Austin McCann. Paul Dixon crosses the ball in from the free kick, Andy Dowie manages to make a clearance.
Paul Dixon produces a cross, Header on goal by Johnny Russell from just inside the area goes over the target.
The assistant referee flags for offside against Andy Kirk. Dusan Pernis takes the direct free kick.
Unfair challenge on Gary Mackay-Steven by Gary Mason results in a free kick. The free kick is delivered right-footed by Willo Flood from left wing, Chris Smith makes a save.
Short corner taken by Andy Kirk.
Unfair challenge on Gary Mackay-Steven by Kevin Rutkiewicz results in a free kick. Free kick taken by Paul Dixon.
Substitution David Graham on for Jordan McMillan.
Free kick awarded for a foul by Robbie Neilson on Martin Hardie. Joe Cardle delivers the ball from the free kick right-footed from left wing, save by Dusan Pernis.
Mark Kerr fouled by Willo Flood, the ref awards a free kick. Free kick taken by Chris Smith.
Martin Hardie concedes a free kick for a foul on Willo Flood. Direct free kick taken by Gavin Gunning.
Booking Martin Hardie receives a yellow card for unsporting behaviour.
Martin Hardie restarts play with the free kick.
Booking Paul Dixon goes into the book for unsporting behaviour.
Foul by Paul Dixon on Andy Kirk, free kick awarded.
Jon Daly takes a shot. Save by Chris Smith.
Gary Mackay-Steven takes the chance to get an effort at goal. Save by Chris Smith.
Assist on the goal came from Willo Flood.
48:44 Goal scored
Goal - Jon Daly - Dundee U 1 - 0 Dunf'mline Jon Daly finds the net with a goal from inside the area to the bottom right corner of the goal. Dundee Utd 1-0 Dunfermline.
Gary Mackay-Steven takes the outswinging corner, Kevin Rutkiewicz manages to make a clearance.
The second half kicks off.
45:00 +1:35 Half time
Half Time The half-time whistle blows.
Outswinging corner taken right-footed by Joe Cardle from the right by-line, Foul by Andy Kirk on Dusan Pernis, free kick awarded. Dusan Pernis restarts play with the free kick.
Outswinging corner taken right-footed by Joe Cardle from the right by-line.
Gary Mackay-Steven challenges Gary Mason unfairly and gives away a free kick. Direct free kick taken by Austin McCann.
Willo Flood takes the outswinging corner, clearance made by Martin Hardie.
Free kick crossed right-footed by Paul Dixon, Gary Mason makes a clearance.
Booking Andy Dowie shown a yellow card.
Free kick awarded for an unfair challenge on Gary Mackay-Steven by Andy Dowie.
Free kick awarded for an unfair challenge on Martin Hardie by Sean Dillon. Free kick crossed by Joe Cardle. Outswinging corner taken by Joe Cardle from the right by-line, Robbie Neilson manages to make a clearance.
Gary Mackay-Steven takes a shot. Save made by Chris Smith.
Unfair challenge on Martin Hardie by Gavin Gunning results in a free kick. Centre by Joe Cardle, Header from deep inside the area by Alex Keddie goes harmlessly over the crossbar.
Unfair challenge on Jordan McMillan by Scott Robertson results in a free kick. Chris Smith takes the free kick.
Kevin Rutkiewicz is penalised for handball and concedes a free kick. The free kick is delivered left-footed by Paul Dixon from right channel, save by Chris Smith.
Booking Kevin Rutkiewicz is booked.
The offside flag is raised against Andy Kirk. Dusan Pernis takes the free kick.
The official flags Joe Cardle offside. Dusan Pernis takes the indirect free kick.
Unfair challenge on Kevin Rutkiewicz by Robbie Neilson results in a free kick. Chris Smith takes the free kick.
Corner taken by Gary Mackay-Steven, clearance made by Martin Hardie. Outswinging corner taken left-footed by Gary Mackay-Steven, clearance by Kevin Rutkiewicz.
The ball is sent over by Gary Mackay-Steven, Close range shot by Robbie Neilson clears the bar.
Paul Dixon produces a left-footed shot from the edge of the area and misses to the left of the goal.
Jordan McMillan gives away a free kick for an unfair challenge on Gary Mackay-Steven. Willo Flood crosses the ball from the free kick right-footed from left channel, clearance made by Kevin Rutkiewicz.
Corner taken by Gary Mackay-Steven, Jordan McMillan makes a clearance.
Kevin Rutkiewicz challenges Gary Mackay-Steven unfairly and gives away a free kick. Free kick crossed by Paul Dixon, Austin McCann manages to make a clearance.
The referee gets the match started.
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