Roberto Soldado stepped up to seal a second 1-0 victory from the spot after Shelvey was deemed to have upended the 22-year-old midfielder.
The pair had previously come together in the first half, with the referee blowing for a free kick, which Laudrup admitted was just inside the area.
"The free kick was given outside and maybe it should have been a penalty, but the penalty in the second half wasn't a penalty," PA Sport quotes Laudrup as saying.
"Tottenham are a very good team but they didn't create many chances on goal and they score from that very light penalty.
"They had a couple of chances at the end of the first half but they were created by ourselves, and apart from that they had nothing."
Defeat means that the Swans remain pointless after two games.