Berbatov scored twice before converting a late penalty, with Park Ji-Sung and Antonio Valencia adding United’s other goals against the visitors who had Conor Sammon sent off late in the first half for what appeared a soft challenge on Jonny Evans.
Chelsea’s faltering title challenge suffered another blow when they were held 1-1 by neighbours Fulham in an early kickoff at Stamford Bridge, the home team registering their third successive league draw.
Juan Mata scored after 47 minutes for Chelsea before Clint Dempsey equalised nine minutes later.
City and United have 45 points from 18 games followed by Tottenham Hotspur (35) who have two matches in hand and visit Norwich City on Tuesday (1930 GMT).
Chelsea are fourth with 34 from 18 followed by Arsenal (32 from 17) who host Wolverhampton Wanderers on Tuesday (1500 GMT).
United’s big win—their second by 5-0 after beating Fulham by the same score on Wednesday—enabled them to halve their goal difference deficit on City who started the day with a plus-10 tally over their neighbours and ended it on plus-five.
Liverpool remained sixth with 31 points after being held to a surprising 1-1 home draw by bottom club Blackburn Rovers at Anfield.
A Charlie Adam own goal put Rovers ahead at the end of the first half before Maxi Rodriguez equalised eight minutes after the break.
Newcastle United ended a run of six matches without a win by beating Bolton Wanderers 2-0 at the Reebok Stadium where Hatem Ben Arfa and Demba Ba scored inside three second-half minutes.
In the day’s other match Sunderland and Everton drew 1-1.