The Jags crashed to a 2-1 defeat to their title rivals, a result that has Allan Moore's side move level on points with the league leaders as Thistle suffered their only Firhill defeat of the Irn-Bru First Division campaign.
Despite Steven Craig giving them a first-half lead, goals from Martin Hardie and Scott Taggart proved decisive for the Ton, but only after the hosts had passed up a number of decent scoring chances as they failed to secure the win.
McNamara was furious when a first-half Craig strike was chopped off after whistler Bobby Madden ruled the striker had fouled Cappielow keeper Derek Gaston.
And the Jags boss reckons it was just one of a number of crucial calls that didn't favour his side as they finished with 10 men following Ross Forbes' dismissal for picking up two bookings.
He said: "A couple of decisions went against us. I thought Stevie Craig's was a totally valid goal. He has not looked at the goalie and he has put it in.
"I thought there were a lot of decisions that were quite baffling. There were bookings for our players when other ones didn't get punished.
"I thought there was a lot of inconsistency there. I didn't actually see Forbes' first one. I didn't know he had been booked, to be honest.
"Even if you look at the booking for Aaron Sinclair where the guy has run into him, the boy then pulls him back after it and the ref gives the free kick, but no booking.
"He then stands in front of the ball in the last minute. You are looking for a bit of parity. I thought a lot of things went against us but, credit to the lads, we kept going and I thought we might have snatched a draw with 10 men."
Even after Craig saw his strike ruled out before heading home a Steven Lawless cross just before the half hour mark, Thistle failed to capitalise on their dominance as Sinclair hit a post, Forbes missed when one-on-one with Gaston and Craig failed to square to Chris Erskine when clear inside the area.
McNamara said: "We had two good chances at the start of the second half, but even in the first I thought we could have been more in front.
"Stevie did brilliantly to set up Ross and the keeper has saved it with his foot and the one with Erskine was deflected and just went past.
"I can't fault them for effort. I am just disappointed with the way it finished because it was a chance for us to extend our lead at the top.
"In the first half, we passed the ball well in difficult circumstances. We knew their threat was going to be second balls, diagonals and set-pieces. We are disappointed to lose."
Despite the afternoon ending poorly for the Jags, there was good news for the Firhill crowd as Stephen O'Donnell and Sean Welsh both returned to the fold after injury spells.
McNamara said: "It was a plus for me bringing Welshy back in. I thought Stephen looked a bit nervy when he came on, but you hope to get a wee reaction. It is good to have them back in the squad."