Josh Street put the Doncaster side, who are now just two points adrift of United with two games in hand, into the lead on 13 minutes.
The visitors drew level on 34 minutes and with conditions deteriorating it looked like ending that way until Brad Vann popped up with the winnerÂ four minutes from time.
Askern looked to be on course for their best win of the season when leading second-placed Retford 2-0 but the home side drew level and then sealed victory with two goals in the last five minutes.
Alex Irwin opened the scoring on ten minutes when putting Askern ahead from the penalty spot.
When Josh Taylor added a second on 38 minutes Retford's unbeaten home record looked to be in danger.
But boosted by a goal within two minutes of the restart, Retford looked a different side in the second half and drew level just after the hour.
Just when it looked as though the lowly Doncaster side would hang on for a deserved point, Retford dashed their hopes with a late brace.
Sutton Rovers became the only second side to beat Division One North leaders Crowle Colts.
A 33rd minute strike by Ellis Pattison provedÂ to be the winning goal as last season's Doncaster Rovers Senior League Premier Division champions climbed a place to second and moved within five points of top spot with two games in hand.
Epworth Town Colts did both sides a favour when putting paid to second-placed Alfreton Town Reserves' 100 per cent record.
Goals by Harrison Coley and Noel Burdett saw them claim a 2-1 win.