Championship Wrap: Top three record victories
Nigel Pearson's men produced a commanding display to cruise to their 16th win of the campaign, David Nugent scoring his 11th league goal either side of strikes from Anthony Knockaert and Jeff Schlupp as Richard Chaplow's goal proved to be nothing more than a consolation for the hosts.
The game was marred by a fan reportedly approaching the assistant referee and grabbing his flag and throwing it to the floor after a goal-kick decision.
Burnley remain four points behind Leicester in second following their 3-2 win against Huddersfield Town.
Striker Danny Ings took his tally to 12 league goals with a double for Sean Dyche's side, however, the hosts were made to work hard for the points against the Yorkshire club.
A second from Ings and a goal from Kieran Trippier finally secured victory for Burnley after the England Under-21 striker's opener had been cancelled out by ex-Burnley man Martin Paterson, who netted again in the 89th minute to give Huddersfield hope.
QPR kept pace in the promotion chase after Harry Redknapp's men came from behind to win 2-1 at Doncaster thanks to a 93rd minute strike from Charlie Austin, but Derby County's promotion hopes were dealt a blow as Jean Beausejour's goal gave Wigan Athletic a 1-0 win at Pride Park.
Stephen Kelly's 95th-minute equaliser earned Reading a 1-1 draw against Nottingham Forest, while Sheffield Wednesday's survival prospects were boosted by a 2-0 home win over Blackpool.
Jordan Rhodes scored his 16th league goal of the season as Blackburn Rovers won 2-1 at Leeds United, who slipped to their second consecutive loss, which allowed Ipswich Town to move into the final play-off spot, despite conceding in injury time of their 1-1 draw with Charlton Athletic.
Elsewhere, bottom club Barnsley drew 1-1 at Birmingham City, Bolton Wanderers grabbed a 90th-minute equaliser to draw 2-2 with Middlesbrough and Stephen Ward's 89th-minute effort spared Brighton and Hove Albion's blushes in their 1-1 draw with Bournemouth.
Meanwhile, Watford's game at Yeovil Town was postponed due to a waterlogged pitch.