Leicester remain firmly on course for promotion to the Premier League after a 3-0 win over Ipswich, while second-placed Burnley also look well placed to reach the top-flight.
Nigel Pearson's Foxes are eight points clear at the top of the Championship and unbeaten in 13 league matches thanks to goals from Jamie Vardy, David Nugent and Chris Wood at the King Power Stadium.
Vardy struck for his 12th goal of the season in the 19th minute and Nugent tapped home for his 18th on the half-hour mark, while substitute Wood netted in the 88th minute.
Burnley kept hold of the second automatic promotion berth, easing to a 3-1 victory over Nottingham Forest at Turf Moor.
Fifth-placed Forest started the day just five points behind Burnley, but Sean Dyche's side were too strong for the visitors.
After Scott Arfield opened the scoring for the Clarets in the 12th minute, Vokes followed up with two goals in 10 minutes as the hosts went into the break well in charge.
Djamel Abdoun hit back for Forest towards the end, tapping in after seeing his penalty saved, but Billy Davies' team could not mount a late fightback.
Third-placed Derby are also in the hunt for automatic promotion and they stayed two points behind Burnley after a hard-fought 1-0 win over Bournemouth.
The visitors were the better side in the first half at the iPro Stadium, but wasted several chances after Matt Ritchie hit a post and Derby made them pay when Chris Martin grabbed his 18th goal of the season five minutes from time.
Martin curled a 20-yard free-kick into the top corner to clinch the points and set up a huge clash with Burnley next weekend.
QPR's hopes of earning a top-two spot suffered a major blow with a 1-0 defeat at struggling Charlton.
The pre-season promotion favourites have now lost three consecutive matches and lie seven points adrift of Burnley.
Sixth-placed Reading's inconsistency returned to haunt them as they lost 1-0 at home to Blackburn who extended their unbeaten run to five games.
Elsewhere, bottom of the table Yeovil boosted their survival bid with a 1-0 win over fellow strugglers Doncaster.
Yeovil are three points behind fourth bottom Millwall, who slumped to a 1-0 loss at relegation rivals Barnsley, who are now only two points from safety.
Wigan won 2-1 at Brighton, Bolton beat Watford 2-0 and Birmingham won 2-1 at Blackpool.
Sheffield Wednesday beat neighbours Huddersfield 2-0, while Middlesbrough drew 0-0 with Leeds.
