Ayr United closed to within a point of second-placed Caley Thistle as Stephen Kelly’s goal sealed victory at Somerset Park.
The on-loan Rangers man settled the game deservedly in Ayr’s favour, with John Robertson’s side listless in attack.
With Dundee United also dropping points at home to Morton, it was a day to forget all round for the Highlanders.
Both sides were unchanged from their Scottish Cup victories last weekend, with Lewis Toshney on the bench for the first time as an Inverness player.
The visitors needed a win to keep Ayr at bay in third and had the first sight of goal, with Jordan White closing down Steven Bell’s clearance but shooting tamely at Ross Doohan.
It took until the 18th minute for Ayr to build anything of note going forward, with a promising foray from Kelly. The midfielder skipped between Charlie Trafford and Brad Mckay, cutting back at the byline for Aaron Drinan but his scuffed effort rolled harmlessly wide.
A combination of Mckay, Kevin McHattie and Mark Ridgers were required to deny the hosts an opener in a frantic exchange that followed, with Kelly, Ross Docherty and finally Alan Forrest all taking aim at the Inverness goal.
The Honest Men were beginning to build momentum and player-manager Mark Kerr’s ball over the top found Drinan, who chested down for Forrest to strike from the edge of the area. Fortunately for the Caley Jags, the shot was straight at Ridgers.
They came closer still just after the half-hour with Michael Moffat meeting Kelly’s corner at the near post, only to direct his header on to the crossbar.
Caley Thistle had a goal disallowed before the break, with White ruled to have fouled Doohan as James Keatings’ free-kick went in, while Forrest fired over before the break.
The half-time interval seemed to do little to dim Ayr’s performance levels. McHattie was required to prevent a Kelly cross reaching Forrest, James Vincent cleared Aaron Muirhead’s shot off the line and Forrest again struck wide, as the home side looked most likely to force an opener.
Charlie Trafford then hit the woodwork for the away side, glancing Keatings’ corner against Doohan’s bar.
But it was Trafford that was culpable at the other end for the opening goal, as Kelly caught him in possession 25 yards from his own goal, advanced and clipped it round Ridgers.
The Caley Jags continued to falter in front of goal, even after introducing Nikolay Todorov as a second striker, with Doohan relatively untroubled in the second period.
Inverness face Alloa next weekend before their Scottish Cup fifth round tie against Livingston.