However judiciary spokesman Jamal Karimi Rad said Frenchman Stephane Lherbier and German Donald Klein were entitled make a further request for parole even though their latest appeal had been thrown out by the court in the southern Hormozgan Province.
"First of all, the reason for the refusal of their appeal was that they received specially reduced sentences" when the verdicts were given at a court in the town of Bandar Abbas in January, Karimi Rad told AFP.
Lherbier, who has a fishing business in the United Arab Emirates, had set out on a trip with his German client in November last year.
The two were arrested near the island of Abu Mussa which is claimed by the United Arab Emirates. They said they had mistakenly used Emirati maps that showed the waters around the island as belonging to the UAE.
Karimi Rad added that as foreigners it would not be possible for the pair to fulfill the normal conditions of parole by staying in Iran and regularly reporting to the authorities.
"And since they cannot fulfill this part of the parole conditions, their request was denied."
"Anyhow, even though their request for parole was denied it does not mean that they can not file another request."
France has already expressed regret over the dismissal of the appeal, saying the orginal penalty was "excessively heavy" in relation to the facts and Paris would continue to press for the men’s release.
Both Germany and France — two countries that have been at the forefront of diplomatic efforts to solve the ongoing standoff over Iran’s nuclear programme — have repeatedly called for the men’s release.