Midfielder claims call by referee Martin Atkinson could have cost Spurs the game while team-mate Gallas wants technology introduced and calls for Uefa to act
Referee Martin Atkinson gave the Spaniard the goal, despite the ball being blocked on its way to goal, with replays clearly showing it had not crossed the line.
The England international felt the call changed the game with the score poised at 1-0 as Tottenham were then forced to chase the tie.
"It's not even a debate, is it really? It's clearly obvious," Parker told Sky Sports.
"It's not even one we can even sit here and say did it/didn't it. It was nowhere near the line. I was in perfect view, I could see four players were covering the line, so how the ball would have got over the line I don't know.
"The linesman said he didn't make the decision and the ref took it upon himself. It was disappointing. Those decisions change games.
"At 2-0 we come out, we chase the game a little bit, we get a goal back [but] we're a bit stretched and at the end of the day 5-1 is a bad result. But that decision is crucial and that's not making an excuse.
"It's a massive part in the game really so we're disappointed."
Defender William Gallas was equally disappointed and believes action now needs to be taken by football’s governing bodies to ensure technology is used to prevent further mistakes.
He added: "I think everybody saw it, it was only the referee who didn't see it.
"For me, I don't know how you accept that goal. There's already some problem so Uefa has to do something.
"They have to do something because now it's a little bit too much and fast tonight for another club. It's not easy."