First-half goals from Glenn Murray, Shane Duffy and Pascal Gross gave the host a third league win in a row against the Red Devils on home soil, a run that stretches back to 1982.

Romelu Lukaku got on the scoresheet for the first time this season, while Paul Pogba converted an injury-time penalty, but the victory was no more than Brighton deserved, with Jose Mourinho's side poor throughout.

Brighton took control in the first half-hour thanks to two goals in the space of 143 seconds, with Murray clipping a delightful finish past David de Gea before Duffy swept home after United failed to clear a corner.

Lukaku, who missed a golden chance at 0-0, nodded in a lifeline for his side but more slack defending saw Eric Bailly bring down Gross, who dispatched his penalty a minute before the break.

With Alexis Sanchez missing the game through injury, Mourinho introduced Marcus Rashford and Jesse Lingard at half-time, but there was little improvement to their attacking display and Pogba's finish from the spot came too late to rescue a result.

The defeat means champion Manchester City has already stolen a march on its neighbour in the title race, after it thrashed Huddersfield Town 6-1 earlier on to make it two wins from two.