Roy Keane called for Manchester United to dump their derby flops as he attacked "shameful" effort levels in the 4-1 defeat to Manchester City.

Along with fellow 1999 treble winners Gary Neville and Peter Schmeichel, Keane said the performance from United was unacceptable at the Etihad Stadium.

Doubles from Kevin De Bruyne and Riyad Mahrez left United to reflect on a wretched afternoon at the home of their neighbours.

A first-half strike from Jadon Sancho had briefly brought United level, as they began the game well enough before fading alarmingly.

Keane said on Sky Sports: "They did give up, and for a player in any game to give up, it's unforgivable really.

"The beauty of top-level sport is there's no hiding place. I know United have done well here the last couple of years. We saw all the United shortcomings today.

"There's ways to lose football matches. We've all lost football matches. But the way United lost it today, they stopped running, they gave up. There are players not running back, that's what I don't understand."

Ralf Rangnick, the interim manager, had led United on an eight-game unbeaten run in the Premier League before this crushing blow.

"The manager will be criticised, and the tactics," said Keane. "But players not running back when you're playing for Man United, it's really unacceptable, it really is. They threw the towel in, which is shameful.

"It's hard when you're out there and you're up against a really good team and they're keeping the ball and you can't get it back, but I go back to it, we see some of the goals and you've got to run back, you've got to tackle.

"United players have shown quality over the years but we've just seen a reflection of where the team is and where the club is. It's just so far behind the other teams."

Sunday's results saw United slip to fifth, as Arsenal went above them with a 3-2 win at Watford earlier in the day.

Keane suspects there is more to United's troubles than may meet the eye, casting a degree of doubt before kick-off on the reason for Cristiano Ronaldo's absence, which was put down to a hip problem.

But he sees no excuse for United's players letting their focus drift.

"Whatever's gone in the dressing room, and we hear noises all the time, and we hear about problems obviously with the new manager maybe coming in, and recruitment," he said.

"But your own bit of pride eventually has to kick in at some stage. There were five or six players who should never play for Manchester United again. Just shameful, shameful that you can't run back and put your body on the line.

"I thought City had a couple of gears to go. They toyed with them. They [United] gave up, and shame on them."

Schmeichel, speaking on BBC Radio 5 Live, felt United were ripe for being picked off and need to look at themselves.

The former goalkeeper said: "I thought Rangnick should have changed things at half-time. He may have had words, but the second half was worse; at no point were United in the game apart from on the scoreline.

"Far too many players are either not good enough, or don't care enough. Having an interim manager means he can't do much; he knows he's not going to be there, so what can he change?

"There are players whose contracts are running down. [Paul] Pogba started the game, big question marks over whether he's going to stay. [Substitute Jesse] Lingard has said he doesn't want to be there. But for all that, Man City showed, in difficult circumstances, that they are the best in the country."