Sunderland are now four points clear of third-placed Middlesbrough and well placed for promotion to the Premiership, but the defeat plunged Tranmere back into a tangled relegation contest they appeared to have escaped from with two successive wins.
Sunderland had lost all six of their previous games at Tranmere, including a FA Cup fourth-round match their in January, but two goals in the first 12 minutes meant an end to that run.
Tranmere started the brighter, with Gary Jones having a close-range header disallowed for offside, but Sunderland went ahead after seven minutes. Niall Quinn found himself in space midway inside the hosts' half and he released Phillips, who slipped the ball past Steve Simonsen from 12 yards out.
Five minutes later, Phillips turned provider, reaching the by-line and delivering a left-foot cross that Nicky Summerbee, starting a game for the first time in a month, rifled into the roof of the net from eight yards.
Chesterfield kept alive their slim chance of reaching the Second Division play-offs with a 2-0 win at Southend.
Peterborough remain on the fringe of the Third Division play-offs after a 1-0 win over the newly-crowned champions, Notts County. Scarborough lifted their promotion hopes with a 3-1 home win over Cardiff.Reuse content