Leyton Orient climbed off the bottom of League One after Dean Cox’s 101st minute goal fired them to a dramatic 3-2 win at Chesterfield.

The hosts opened the scoring when they were awarded a penalty and Jay O’Shea fired home. But the O’s responded well and were rewarded when David Mooney tapped in the equaliser.

Orient fell behind for a second time after the break in unfortunate circumstances as defender Elliot Omozusi fired past his own keeper. But the visitors equalised for the second time as Mooney netted again.

The O’s struck with virtually the last kick of the game as Cox netted to give them their first win of 2015 and a huge lift in their battle to avoid relegation.

Fabio Liverani made three changes from the side beaten at home to Notts County. Captain Nathan Clarke returned to the side in place of Mathieu Baudry.

Omozusi was also handed a recall in place of Scott Cuthbert while Cox started ahead of Kevin Lisbie.

It was a relatively quiet start to the match but it came to life when the visitors conceded a penalty. Clarke brought down Caolan Lavery in the area and O’Shea stepped up to send Alex Cisak the wrong way.

The O’s almost responded immediately but a shot from Cox was saved by Tommy Lee. But the hosts also went close through goalscorer O’Shea whose effort was held by Cisak.

Orient had another opportunity when Mooney snatched at a volley and it drifted wide.

But the visitors equalised in the 35th minute when Cox set up Mooney for a simple tap-in.

Orient finished the half the stronger side but suffered another blow when they fell behind again in the 54th minute.

Armand Gnanduillet sent in a cross and Omozusi volleyed the ball past his own keeper.

Liverani brought on Marvin Bartley for his first appearance since November in place of Josh Wright. Ryan Hedges also came on in place of Bradley Pritchard.

But Orient again levelled the match after a long ball released Mooney and he fired past Lee.

Mooney was not given the chance to complete his hat-trick as he was taken off in the final ten minutes for Shaun Batt.

The O’s had a late chance to snatch the points but captain Clarke was denied when his header was saved by Lee.

There were eight minutes of injury time but the hosts had to finish with ten men after Ian Evatt limped off with an injury.

Gary Sawyer fired in a shot deep into injury time but Lee managed to save the defender’s effort.

But there was still time for a dramatic winner in the 101st minute as Lee dropped a cross allowing Cox to tap in for a potentially priceless goal.

Chesterfield: Lee; Clucas, Raglan, Evatt, Darikwa; Duffy (Jones, 76), Morsy, Ryan (Humphreys, 79), O’Shea; Gnanduillet (Harrison, 83), Lavery

Subs not used: Carter, Chapman, Banks, Dieseruvwe

Leyton Orient: Cisak; Sawyer, Clarke, Lowry, Omozusi; Cox, Vincelot,Wright (Bartley, 58), Pritchard (Hedges, 67); Dagnall, Mooney (Batt, 84)

Subs not used: Baudry, Lisbie, McAnuff, Woods

Attendance: 6,524(285 Orient fans)

Referee: Tim Robinson