Ahead of Netanyahu's contentious speech to U.S. Congress, Meir Dagan said that "the person who has caused the greatest strategic damage to Israel on the Iranian issue is the prime minister".
Dagan has been a fierce critic of Netanyahu's approach to Iran, emerging as a key opponent of Zionist military attack threats against its nuclear facilities.
He said Netanyahu's trip to Washington, over White House objections, is pointless and counterproductive.
Dagan directed the Mossad from 2002 to 2010, a period when it reportedly carried out covert attacks against Iranian nuclear scientists and unleashed cyber-attacks.
His comments come days after a leaked intelligence cable from 2012 revealed a rift between the occupying regime of Israel's top politicians and its intelligence agency over Iran.
Mossad contradicted Netanyahu's warning to the UN General Assembly that Iran was nearing completion of building a nuclear bomb, in the classified document, which was revealed as part of The Spy Cables, a cache of hundreds of intelligence documents leaked to Al Jazeera's Investigative Unit.
In Occupied Palestine, Netanyahu is being accused of cynically turning the speech into a campaign stop ahead of March 17 elections, insisting on confronting U.S. President Barack Obama to distract from scandals and domestic issues dogging his re-election bid.
The uproar has even pushed aside debate over his key argument that Iran's nuclear capabilities will be left largely intact.
The occupying regime’s media and political opponents have lambasted the decision to flout the White House, and even some allies who support Netanyahu's message have criticized the approach.
The U.S. administration is refusing to meet with him and appears to be considering ways of undercutting him.
The White House has already said it was scaling back on the intelligence it typically shares with Israel, some pro-Zionist Democrats are skipping his speech and Jewish American groups have spoken out against the visit.