With two matches of their 22-game season left to play, the Red Devils have 50 points, seven more than reigning champions Chelsea.
Manchester City are second on 44 points, while Arsenal remain fourth on 41 after a 1-0 win over Leicester City on Saturday.
United dominated from the kick-off but it took until the 32nd minute for Leah Galton (28) to open the scoring, pouncing on a poor back-pass from Amy Turner (31) and slotting the ball home.
Alessia Russo (24) added the second three minutes later with a close-range volley and Nikita Parris (29) wrapped up the three points in the 53rd minute, hooking the ball home after the Spurs defence failed to deal with a Galton cross.
In Sunday's late kickoff, Chelsea's Norway international Guro Reiten (28) opened the scoring and Pernille Harder (30) netted with her first touch off the bench as the Londoners slammed five goals past Everton in the opening 45 minutes.
Harder and Erin Cuthbert (24) added to the tally in the second half as the Blues hammered sixth-placed Everton.
Elsewhere, Rachel Daly (31) netted a hat-trick in Aston Villa's 5-0 thrashing of bottom side Reading to move to the top of the scoring charts on 20 league goals for the season.
Brighton & Hove Albion climbed to ninth with 16 points with a 1-0 home win over West Ham United, who they trail by a point.
Reading prop up the 12-team table with 11 points, two behind Leicester, who have a game in hand, and three off Spurs who they visit in their next game on May 27. One side will be relegated.
