"Under these circumstances, all statements saying that the candidate from The Republicans or the one from National Front have been listened to by the judiciary constitute pure speculation, at best, and a desire to manipulate reality, at worst," Urvoas said in a statement posted on the French Justice Ministry's website.
Urvoas also said in his statement that a decision about putting someone under surveillance can only be taken by independent magistrates in charge of a relevant investigation.
"Since 2012, the government has not intervened in any form in the course of the judicial procedures," the statement said.
Earlier in the day, Le Pen told Europe 1 broadcaster, when asked about possible wiretapping that she was "not naive" and that she had known for decades that "the authorities use this type of methods."
Latest polls show Le Pen likely to make it into the second round of the presidential election with independent Emmanuel Macron as her rival there. Fillon lost some standing after a scandal broke out over his relatives' employment in the parliament and allegations that his wife may not have done the work she had been paid for.
The first round of the presidential election is scheduled for April 23, while the run-off between the two top candidates is slated for May 7.
