Stepney was accused of passing Ferrari information to McLaren chief designer Mike Coughlan, who has since been suspended by the world championship leaders.
"I did not take any designs away from Ferrari. Someone passed on the designs but it wasn't me," Stepney told Italy's La Repubblica. "I do not want to involve other colleagues. I know one part of the story, not all. Ferrari know the whole story."
The International Automobile Federation (FIA) ruled last week that although McLaren had Ferrari data in their possession, there was insufficient evidence that they had gained any benefit from it, therefore no penalty was imposed.
However, the FIA announced on Tuesday there would be an appeal. McLaren risk exclusion from the 2007 and 2008 championships while Stepney and Coughlan may also face bans.
Ferrari have taken legal action in Italy and England against Britons Coughlan and Stepney.
As well as starting action against Stepney in Italy for the spying row, Ferrari have gone to court after accusing him of sabotage.
A mysterious powder was allegedly found around the petrol caps of their cars days before the Monaco Grand Prix in May.
Powder also turned up in Stepney's pocket but he said he was set up.
"They put the powder in my trouser pocket while I was taking a shower," Stepney said without stating who he meant by "they".
"I am ready to be heard (by the court) at any moment," added Stepney, who said he had already found another job far away from Italy and Formula One.
In a statement on Tuesday, Ferrari said: "The board gives its full authority...to initiate and continue any necessary legal action, in the name of the company, in addition to those legal actions already underway."
McLaren are 27 points clear of Ferrari with seven races remaining in a championship led by their 22-year-old British rookie Lewis Hamilton.
His team mate, double world champion Fernando Alonso, is two points adrift, with Ferrari's Brazilian Felipe Massa third, a further nine points back.
