Wycombe defender Giles Phillips was controversially sent off as Peterborough ran riot to condemn Ainsworth's side to consecutive 4-0 defeats away from home.
QPR loanee Phillips was judged to have impeded Sammie Szmodics in the 21st minute and was sent off before Ivan Toney scored from the resulting penalty.
“I'm really disappointed with the decision that went against us – extremely disappointed. But I'm not going to say anything that gets me in trouble and compounds this miserable night,” Ainsworth reflected.
“A couple of the goals really got to me, especially that first penalty but the less said about that the better.
“I think 2-0 would have been acceptable, I know that sounds weird but 4-0 not so much. We gifted them a couple of goals.”
Toney's 17th League One goal of the season capped of a miserable night for The Chairboys, who missed the opportunity to go top and remain second on goal difference behind promotion rivals Rotherham.
“Ivan Toney showed why he is one of the top strikers in the league. He dominated and that's not good enough,” Ainsworth continued.
“We've gone from being pretty impenetrable to now leaking a few goals.”
The defeat comes just 10 days after Wycombe shipped four in defeat at the Stadium of Light.
Peterborough manager Darren Ferguson disagreed with Ainsworth's assessment of the decision and was left in no doubt that the referee made the right call.
“It's a penalty kick,” Ferguson asserted.
“Obviously we got the break with the referee sending him off as well but we're probably due that.
“We needed that result because we've been on a bad run. That should give the players a lot of confidence.”
Victory at the ABAX Stadium snapped a seven-game winless streak for Peterborough, who climb to eighth just one point outside the play-off places.
