Derek Lilley grabbed a last-gasp winner against 10-man St Johnstone to all-but guarantee Dundee United their Premier League survival and send St Mirren down to Division One.

The Paisley outfit now need a miracle on the final day of the season to stay in the top-flight - needing United to lose at Aberdeen while beating Motherwell by more than 10 goals.

But the men from Tannadice snatched a vital victory from the jaws of defeat after going into the dressing room at half-time two goals down after goals from David McClune and Paul Hartley.

A missed penalty from Charlie Miller made the agony even worse and looked to have thrown St Mirren a lifeline.

But Miller sparked an amazing fightback with a goal after the sending off of Hartley.

Craig Easton and Lilley turned the game on its head to leave them three points ahead of St Mirren going into the final day of the season.

But United suffered a early body blow in their bid to secure their Premier League survival.

Hartley's shot was blocked by Jason de Vos and the recalled McClune curled a wonderful effort from the right of the area over the despairing United goalkeeper Paul Gallacher and into the top corner.

The youngster was only in the side because of an injury to Stuart McCluskey and he took advantage of some nervous defending by United.

But the visitors came storming back and almost grabbed the equaliser in the 22nd minute when Easton found space in the box, but he drilled his effort straight at Alan Main.

The St Johnstone frontmen were causing United all sorts of problems and David Partridge was fortunate not to go into the book in the 26th minute for a lunge on goalscorer McClune.

But United were granted a wonderful opportunity to draw level from the penalty spot a minute later when Darren Dods tripped Miller in the box.

The former Rangers midfielder was brave enough to step up and take responsibility himself, but he screwed his weak right-foot effort well wide of Main's right post.

That prolonged the agony for the travelling Tangerine fans and that was almost compounded in the 29th minute when Dods got on the end of Momo Sylla's corner, but he headed straight at Gallacher from five yards.

But United's afternoon was to go from bad to worse when they fell further behind five minutes before the break.

John Paul McBride played Sylla through on goal and he poked the ball into the path of Hartley, who cooly slotted the ball past the advancing Gallacher.

The former Hibernian player celebrated in front of the visiting fans, which incensed the travelling support and earned him a booking which was to prove costly.

United manager Alex Smith replaced Partridge with Jamie Buchan at the break and as expected they came out fighting.

And the visitors were thrown a lifeline three minute after the break when Hartley was shown a second yellow card for a reckless two-footed lunge on Miller.

Danny Griffin tried to reduce the deficit from the free-kick with a right-foot shot over the St Johnstone wall from 22 yards, but Main was equal to it and made the save.

Miller rejoined the field of play moments later after receiving treatment, much to relief of the United fans and team-mates.

The match was becoming nasty and Sylla went into the book for a clumsy challenge on Buchan in the 53rd minute.

United had Derek Lilley cautioned for a foul on Marc McCulloch and then inevitably Miller suffered a similar fate for clashing with St Johnstone skipper Jim Weir.

But they kept going in a frantic search for goals and Jamie McCunnie and Buchan both fired efforts over the bar.

But they were back in the game with 65 minutes gone as Main allowed Lilley's cross to slip through his grasp and Miller made amends for his missed penalty by heading home at the far post.

Minutes later and Lilley let fly with a left-foot effort which flew just past the upright and Main produced a marvellous save from Miller from point-blank range.

Lilley went close on two occasions as United turned up the heat on the 10-man Saints.

But they grabbed the important leveller with nine minutes remaining when Easton emphatically headed home Miller's cross.

Main pulled off a superb save to deny Lilley in the 86th minute as St Johnstone hung on for their lives.

But with just two minutes remaining United grabbed a dramatic winner when Lilley stabbed the ball home in a crowded area to break St Johnstone and St Mirren hearts.

The final whistle sparked a pitch invasion by the relieved United supporters, who celebrated their SPL survival.