The hosts scored the only goal of the game after 19 minutes when Weston went down under a challenge from Rovers keeper Conrad Logan as he raced towards goal, leaving Gary Alexander to make no mistake from the spot.
But Penney said: "The good thing about modern technology is that I can watch the penalty decision two or three times and it was never a penalty. He (Weston) has over-stretched and then jumped over the top of our keeper.
"It is gamesmanship or another word which I will not use. Equally the officials let Brentford waste time and didn't add on enough time at the end and they got it wrong again and again here."
Penney added: "We really carried the game to Brentford and we created plenty of chances. The performance was excellent and my players are disappointed, frustrated and angry at the outcome.
"We had all the pressure, all the possession and the momentum was with us but we just couldn't find the net. It is disappointing but if we keep taking the game to sides like we did here then the results will come."
Source: PA
Source: PA