The Hoops begun today one point in arrears of title rivals Rangers with a game in hand but ended it the same margin behind but equal on games played as Inverness took everything to them to win 3-2 at Tulloch Caledonian Stadium.
It started badly for Celtic when in the 7th minute Adam Rooney went for a backheel from Shane Sutherland's cross from the right with his attempt from a tight angle ricocheting in off Celtic defender Charlie Mulgrew to give the home side an early lead.
But less than two minutes later, Kris Commons got a leveler when he received a pass from Emilio Izaguirre before running at the Caley defence and whipping his left-footed shot home past Ryan Esson from just outside the area.
After the equaliser it seemed as though the Hoops had settled more but Inverness continued to come at the title chasers and it turned in their favour when Grant Munro controlled a poorly-cleared corner just inside the box before smashing home past Fraser Forster to make it 2-1 to the home side in the 53rd minute.
Just as the season seemed to be getting away from the Hoops, things got even worse in the 65th minute when Sutherland got in on the act with a neat strike from 18 yards to give Terry Butcher's men a commanding lead.
Celtic came at Inverness hard in the final 25 minutes and had a host of chances to get back into the contest and although they did peg one goal back, through Commons' injury-time penalty, it was not enough as they handed the lead and the Premiership ascendency to their Old Firm foes.