Two first-half goals from Katie Zelem and a third from Mollie Green at the start of the second period set Casey Stoney's team on track, before late headers from Jess Sigsworth and Leah Galton made absolutely sure of the points.
The top-of-the-table clash started brightly, with both sides keen to get forward from the outset and Spurs demonstrating why they have been the Reds’ main challengers throughout the season.
It was United who opened the scoring though, with just three minutes on the clock. Zelem picked the ball up just outside the area and took aim with a long-range effort.