The accusations were published by El Diario on Friday, just three days before the Roja kick off their campaign against Czech Republic.
According to the testimony, Iker Muniain and another, unidentified player from Spain’s Under-21 team were involved in the alleged events, which took place in 2012.
While De Gea is not accused of being present at the scene, the witness stated that the current Manchester United keeper organised the evening with Torbe – whose real name is Ignacio Allende Fernandez.
“I am the first to be surprised by this story, it is complete lies and falsehoods,” he responded in a press conference.
“This gives me more strength to be with this team, it is now in my lawyers’ hands.”
De Gea rejected any notion that he would be dropping out of Spain’s Euro 2016 challenge.
“I am going to stay with the national team, I have the strength and my team-mates’ support and I want to fight for the Euros,” he affirmed.
De Gea later trained as normal with the Spain team at their La Rochelle base with their Group D opener coming on Monday afternoon when they tackle Czech Republic in Toulouse.