The Dark Blues remain stranded at the foot of the table, as Matt Lockwood sees in red with new interim boss John Brown looking on as they suffered a 13th game without a win
The Dark Blues arrived in Glasgow in turmoil after the unpopular appointment of John Brown as interim manager following the sacking of Barry Smith and their chances took a huge dent when Matt Lockwood was sent off just after the break.
Neil Lennon rang the changes from the side the drew at St Johnstone, with Adam Matthews, Charlie Mulgrew, Victor Wanyama, Kris Commons and Lassad Nouioui all dropping out to be replaced by Thomas Rogne, Beram Kayal, Anthony Stokes, McGeouch and Forrest.
Dundee coach Ray Farningham took control of the side and had to make one change from the side that lost to Aberdeen, with on-loan Celtic defender Lewis Toshney ineligible, meaning that Kyle Benedictus was forced to step in.
The Dark Blues thought they had claimed the lead within the first five minutes as Gary Harkins curled a free kick wide on the left, which beat Fraser Forster at his near post, but somewhat strangely the assistant referee ruled that John Baird was offside and interfering with play, which saw the goal ruled out.
It was the league leaders who took control of the game as former Celtic keeper Rab Douglas spilled a cross from the left by Emilio Izaguirre directly into the path of Ledley, allowing the Welsh international the simplest of tasks to stroke the ball into an empty net.
Celtic continued to force the issue in search of a second, with Hooper receiving the ball from Forrest in the middle of the Dundee half and the English striker powered forward before trying his luck from range, but Douglas managed to batter the ball away.
Harkins then had two efforts in the space of a minute, as first a long range strike from the midfielder was tipped over by Forster and then from the resulting corner he watched his header smack off the bar.
The second half started miserably for the visitors, as within three minutes of the restart, Lockwood, who came on as a substitute for Brian Easton at the break was sent off for hauling down Hooper inside the box and Forrest stepped up to slot the ball home.
Victory was secured for the Glasgow giants just before the hour mark, as Stokes played in a superb cross from the left, directly onto the head of McGeouch, who sprung to rise and direct the ball beyond Douglas in the Dundee goal.
Ledley then claimed his second goal of the game, as he got onto the end of a cutback from Stokes and slammed the ball past the helpless Douglas to claim Celtic’s fourth of the game.
Lennon’s side celebrated going 21 points clear at top late on as Hooper came in at the back post after a ball from Ledley to smash home and claim Celtic’s 100th goal of the season.