Gareth Williams levelled in injury-time to deny Grimsby what would have been a crucial victory in their bid for First Division survival.

The bottom-placed Mariners are locked in a relegation dogfight with Brighton, Stoke and Sheffield Wednesday and survived a vicious Forest onslaught before Williams popped up to poke home Marlon Harewood's cross.

Alan Pouton had put the Mariners ahead two minutes after the break after Paul Groves' 44th-minute equaliser cancelled out Andrew Reid's deflected opener.

Forest defender Jon Olav Hjelde had the first chance of the game after seven minutes when he escaped his marker but he sent his free header from Reid's corner straight at Danny Coyne.

John Thompson's header from Riccardo Scimeca's corner rolled agonisingly across the face of goal on the quarter hour as the hosts controlled the opening exchanges.

Then on 22 minutes Forest took the lead. Captain Scimeca rolled a free-kick to Reid and his 30-yard effort took a wicked deflection off Pouton and flew into the net, leaving Coyne rooted to the spot.

Darren Huckerby saw an angled drive 10 minutes before the break come back off the post in one of the few clear-cut chances, although Harewood had drifted into an offside position and the goal would not have stood.

Grimsby struggled to create anything going forward and Pouton's weak shot from 25 yards was all they could muster before silencing the home crowd with the equaliser two minutes before half-time.

The Mariners patiently strung together 14 passes before Darren Mansaram escaped down the left and his low pull back was not dealt with by the Forest rearguard, allowing Groves to ghost in and stab the ball past Darren Ward.

Grimsby stunned their hosts again three minutes after half-time when Pouton fired them ahead.

John Oster swung over a free-kick from the right wing, Ward did not get enough on his attempted punch clear and Pouton drilled the ball back into the unguarded net.

Forest battled to get back into the game and Michael Dawson came close from Scimeca's corner but his header drifted narrowly wide after 58 minutes.

The highly-rated youngster had another opportunity moments later but again could not direct his header on target.

Paul Hart threw top scorer David Johnson on for Hjelde after an hour to try and inject more firepower into his misfiring side.

And it was Johnson who had the best chance to level but his header from Harewood's driven cross flew narrowly over.

Johnson was also presented another chance through the pace of Harewood but could not keep the effort down and Williams blazed over from Johnson's header as Forest threw everything at Grimsby.

It looked as if the Mariners were going to hold on for a vital victory but, a minute into injury time, Darren Huckerby found Harewood in space on the left side of the box and his cross was turned past Coyne by Williams.

Teams

Nottm Forest: Ward, Louis-Jean, Dawson, Hjelde (Johnson 64), Brennan, Thompson, Scimeca, Williams, Reid, Harewood, Huckerby.

Subs Not Used: Jess, Roche, Oyen, Doig.

Booked: Huckerby, Scimeca.

Goals: Reid 23, Williams 90.

Grimsby: Coyne, McDermott, Ford, Santos, Gallimore, Campbell, Groves, Pouton (Barnard 85), Richard Hughes, Oster, Mansaram (Livingstone 85).

Subs Not Used: Allaway, Chettle, Bolder.

Goals: Groves 44, Pouton 48.

Att: 25,507

Ref: S Tomlin (E Sussex).