ElBaradei "has been quite negligent in revealing all the difficulties that the monitors have in Iran and also in not exposing the full picture of the deception and acceleration of (its) illegal military nuclear activities," the official told AFP on condition of anonymity.
"There is here a dereliction of duty against the mandate" of the head of the International Atomic Energy Agency, he said. "His attitude has always been… quite duplicitous during his entire tenure."
It marked the latest Israeli criticism of ElBaradei, who is to step down in December. The Jewish state has often accused him of being lax towards arch-enemy Iran and asked for him to be fired in 2007.
Last week, the Haaretz newspaper quoted unnamed Israeli officials as saying the IAEA was refraining from publishing data obtained in recent months that indicated Iran was pursuing information about weaponisation efforts and a military nuclear programme.
ElBaradei has said the UN watchdog does not have any evidence suggesting Iran is developing a nuclear weapons programme.
But Haaretz cited officials as saying the new evidence was presented to the IAEA in a classified annex written by its inspectors and said to have been signed by the head of the inspection team in Iran.
The document was not included in the final report, it said.
British, French, German and US officials are pressuring ElBaradei to publish the information, the official said.
Widely considered to be the Middle East's sole if undeclared nuclear armed power, Israel suspects Iran of trying to develop atomic weapons under the guise of a civilian nuclear programme, a charge Tehran denies.
Israel considers the Islamic republic to be its main foe following repeated statements by President Mahmoud Ahmadinejad that the Jewish state is doomed to be "wiped off the map."
