Furious Mark Kerr admits he couldn't believe his team's collapse as Ayr blew a two goal Cappielow lead at the death.
United, despite playing most of the second half with ten men after Aaron Muirhead's red card, looked home and hosed after a dominant display.
But three goals in the last seven minutes saw defeat snatched from the jaws of victory - and left Kerr livid.
He said: "I can't believe how we've defended at the goals...we've just switched off and made basic mistakes.
"It was like panic stations at the back when they've lumped high balls at us late on.
"But we should have had more than enough to deal with that, it's just poor positioning on our part not to deal with it."
The boss added: "It's so hard to take. There was so much to be pleased with in that game and then we've gone and made such basic errors.
"We chucked two points away at Inverness last week and now we've done this.
"To be sitting with only four points out of nine after how we've played is really disappointing."
Ayr were by far the better side for most of a contest played out in awful conditions.
After getting to grips with the driving rain and swirling winds in the first half, they went on to control the opening period.
Cammy Smith and Bruce Anderson both had efforts saved before Michael Moffat went close to his 100th goal with a shot over the top.
Anderson went agonisingly close to the opener on 24 minutes when his shot on the turn smashed the inside of the post and rolled across the line to safety.
But Ayr eventually got their opener when Anderson charged down the left and hit the byline before crossing for Smith and he forced an own goal at the nearpost from Lewis Strapp.
Smith was everywhere during the first half and fired just wide on 44 minutes before teeing up Anderson for a shot which flew just wide.
And if Ayr feared their missed chances may come back to haunt them, the signs were ominous just seven minutes after the restart when Muirhead saw red for a lunge on Josh McPake.
But for all their numerical advantage Morton posed little threat as the second half wore on and only Aidan Nesbitt's free kick - saved by Viljami Sinisalo - had Ayr in any bother.
With Jordan Houston replacing Moffat to add more steel, United began to weather the storm and then looked to have killed the game on 72 minutes.
Good work by Luke McCowan on the edge of the box saw him play in Smith and he showed composure to slot past Aidan McAdams.
And Ayr could even have grabbed a third but sub Innes Cameron couldn't get his shot away as the 'Ton defence scrambled clear.
Then came the incredible last seven minutes as, first, Gary Oliver grabbed what looked to be a consolation after firing home when Ayr had failed to clear a cross into their box.
But less than two minutes later, the game was all square as another high ball caught out Paddy Reading, whose loose header flew straight across his own box and into the path of Cameron Blues who fired home.
And as Ayr rocked, Morton incredibly bagged a winner as Brian McLean pumped another long ball into the box and Strapp arrived to head home into the bottom corner.
Morton boss David Hopkin said: "We were playing against a very good Ayr United team who have quality players they've taken from Premier League clubs.
"In the first half we got a bit of a runaround and I asked the players for a reaction at half time.
"And I certainly got that. The character we have at this club was there for all to see."