They gifted Montrose the opener in the 35th minute when Michael McGowan put through his own net.
Terry Masson's 51st-minute strike for the home side sealed a comfortable victory.
Clyde climbed to second and trail East Stirling by only two goals after a hard-fought 2-1 success at Stirling Albion. David Marsh's crisp 17th-minute strike put Clyde ahead and Scott Ferguson doubled their lead before half-time.
Nine minutes after the break, Bradley Coyne's powerful drive halved Stirling's arrears but a leveller proved elusive despite Clyde's Gavin Brown being sent off in the closing stages.
Annan Athletic are two points further back in third place after a 3-2 comeback win at Elgin City.
Early goals from Craig Gunn and Brian Cameron looked to have flattened Annan after 15 minutes.
But Peter Weatherson's header cut Annan's deficit before Josh Todd equalised. The turnaround was complete when Kenny Mackay buried a last-minute winner.
Bottom club Queen's Park remain without a league win as a comical late goal gifted Albion Rovers a 1-1 draw.
The hosts scored in the 36th minute when Lee Davison finished a flowing move involving Blair Spittal and Sean Burns. With only two minutes left, the home side's Anthony Quinn put the ball in his own net.
Peterhead and Berwick Rangers shared the spoils in a lively 1-1 draw at Balmoor. Stephen Tulloch fired Berwick into an 18th-minute lead but Rory McAllister's penalty earned a point for Peterhead.