Dwight Gayle had already rattled the crossbar with a volley when he stunned Elland Road with a blistering opening goal in the 15th minute.
Leeds subsequently raised their game but had to wait until just shy of the hour mark before teenage defender Sam Byram turned home Stephen Warnock's corner at the far post to ensure it finished 1-1.
Posh, who thrashed Millwall 5-1 and won 3-2 at Blackburn in their previous two away games, leapfrogged Wolves and Bristol City but failed in their bid to climb out of the bottom three.
"It's not a good point," said Ferguson, who revealed he will be having a meeting with referees' boss David Allison over a series of decisions throughout the season that he feels have gone against his side.
"It's really disappointing that we dropped two points. It was a great opportunity to get three points and out of the last three draws I would say this was the biggest opportunity. But unfortunately we only take a point. We had seven or eight chances to get the second goal and we've not taken them."
Ferguson was also aggrieved Warnock was not shown a red card for his 70th-minute challenge on Kane Ferdinand on the edge of the box.
"I've just seen the referee and to be fair he said he'd watch it again," Ferguson said. "You've got to be denying a goalscoring opportunity and if that's not a goalscoring opportunity I don't know what is. But to be fair to the ref he said he'd phone me and apologise.
"That might stop us going down and it might not stop us staying up, but at least he's done that.
"If it happened at the other end the referee would not have got out of here alive if he hadn't given a red card."