With a number of sides involved in the FA Cup, the Foxes moved eight points clear of second-placed QPR thanks to second-half goals from Jamie Vardy and Ritchie de Laet.
Ipswich's first win in seven matches closed the gap to the play-off places to two points after a 2-0 victory over Reading, moving them into seventh - just one spot behind the Royals.
Darryl Murphy opened the scoring just past the hour with a shot off the underside of the crossbar and substitute Paul Anderson made the points secure in the 90th minute.
Derby required an 86th-minute equaliser from on-loan Chelsea forward Patrick Bamford to ensure they left Ewood Park with a point.
Rudy Gestede gave Blackburn the lead just after half-time but Bamford struck to deny their hosts victory.
Striker Billy Sharp also scored late on his return to Doncaster to deny caretaker Blackpool manager Barry Ferguson a winning start at Bloomfield Road.
Substitute Andy Halliday scored on his debut on loan from Middlesbrough to put the Seasiders, who sacked boss Paul Ince this week, ahead.
However, Sharp, back at Rovers for a third spell after leaving Southampton on loan, equalised five minutes from time for a share of the spoils in a 1-1 draw.