United were desperately searching for an equaliser at Old Trafford against Tottenham Hotspur when Lloris came racing out to meet Young, who had charged into the area.
Young got to the ball first, sending an effort towards goal, but was then forced to leap above Lloris to avoid being clattered by the Frenchman.
The winger suffered a bang on the left shoulder as he tumbled to the ground, yet Webb remained unimpressed, rejecting United's penalty claims - much to Moyes' disgust.
"It was scandalous," said Moyes.
"If you follow through on a player anywhere else on the pitch with your foot high, it would be a sending-off and a red card. You couldn't do that anywhere else.
"The goalkeeper comes out, Ashley Young gets the ball before him and he follows through.
"It's an incredible decision which didn't go our way, in fact probably the one of the worst I think I saw."
Moyes' fury was compounded by Adnan Januzaj being booked, seemingly for diving, for the third time this season, even though the challenge from Danny Rose which preceded the fall was a pretty firm one.
"Have you seen that decision? That is a terrible decision," said Moyes.
"Adnan has got bumped. The boy has tried to edge him off the ball."
In addition, United felt Spurs could have been reduced to 10 men when Lloris appeared to handle outside his own area early on.
On that ruling, Moyes was more forgiving.
He rejected the notion that Webb may have been overcompensating for claims on social media - totally unfounded - that the South Yorkshire official is a United fan.
"I don't know anything about that," said Moyes.
"All I can tell you is that (Lloris' challenge on Young) is a stonewall penalty kick.
"If that isn't given a penalty kick, I don't think we will get any more in the league this season."
Clearly, Moyes feels referees' chief Mike Riley needs to step in.
"It is reckless, it is late, it is in the penalty box," said Moyes.
"I don't know what else you can say.
"You'd hope the people who put the referees out there would have a look at it and see if they think the referees are doing as well as they can be."
The row can only partially obscure a fourth home defeat of the season for United, the quickest they have achieved such a sorry position since 1986.
Despite dominating possession, chances were hard to come by and Emmanuel Adebayor put Tottenham ahead with a precise header before the break.
Antonio Valencia's limitations as a makeshift full-back were exposed by Christian Eriksen after half-time and although Danny Welbeck pulled one back almost immediately, the equaliser would not come as United dropped to seventh, leapfrogged by their opponents.
"I am not frustrated," said Moyes. "I thought we played really well.
"Today was a defeat of course, but we deserved to win, or at worst draw."
Wayne Rooney completed the full 90 minutes despite looking some way short of match fitness as he manages a groin problem that may mean him sitting out further games after missing Saturday's trip to Norwich.
"If I could (rest him), I would," said Moyes. "But the games are coming thick and fast.
"He has missed a couple with his groin and may well miss some more in the games coming up."
It now seems impossible for United to retain their Premier League title, with even fourth-placed Liverpool five points ahead.
With FA Cup and Capital One Cup matches against Swansea and Sunderland to come United at least do have a break from the rigours of a Premier League campaign they have found so troublesome.
Yet Moyes insists the latest setback will not affect his January transfer window plans.
"The result today would never have any effect on what we do, whether in January or the summer," he said.
"It wasn't our day but it won't change the way we go about our business."