Motherwell manager Mark McGhee was incensed by a disallowed goal scored by Scott McDonald during his side's 2-1 loss to Celtic.
McDonald netted from Louis Moult's cross, but was flagged offside.
"Once again we feel we've been let down by the officials, which is horrendous given the importance of the situation," said McGhee.
"It's a shocking decision. We have video replays, we know it's onside, we know it's level."
McGhee appeared to refuse to shake hands with counterpart Ronny Deila on the full-time whistle but later told BBC Scotland the snub was due to a "misunderstanding" on his part and that it had been resolved.
"What actually happened was, at the beginning of the game, I felt as if when I went over to shake hands with the Celtic staff they blanked me," explained McGhee.
"I've spoken to Ronny about it and it was a total, 100% misunderstanding on my part, and I accept totally he didn't see me. That's fine, and he and I have shaken hands."
Defeat leaves the fourth-placed Fir Park side's top-six berth uncertain, with Dundee, St Johnstone and Partick Thistle all capable of usurping them in Saturday's later kick-offs.
"We'll take what comes," said McGhee. "If we're in the bottom six, we'll deal with it. If we're in the top six, that's fantastic.
"We've come close. St Johnstone, Dundee, Partick Thistle - they've had great seasons as well and if they all end up in the top six then good luck to them and well done, because they deserve it every bit as much as we do."