It's as much a Washington tradition as fireworks on July 4.

The blockbuster memoir is a rite of passage for retired power brokers keen to settle scores, polish legacies and replenish bank accounts left barren by years of public service.

Leon Panetta, the former defense secretary and CIA chief is the newest member of the exclusive but expanding club of former Barack Obama confidants to take pot shots at the president from the pages of a fat new tome.

Panetta, renowned as a Washington wise man, spills an unflattering verdict on Obama's leadership in "Worthy Fights."

He sees a president whose weakness is a frustrating reticence to engage his opponents "and rally support for his cause."

Obama, Panetta writes, lacks fire, "relies on the logic of a law professor rather than the passion of a leader" and occasionally "avoids the battle, complains and misses opportunities."

Hawking his book on CNN, Panetta complained that White House aides, eager to be rid of the Iraq war, failed to use US leverage to convince Baghdad to accept a post-war US stabilization force.

He criticized Obama for dithering on whether to arm Syrian rebels, contributing to the rise of the Islamic State group.

Panetta's criticisms mirror those of his Pentagon predecessor Robert Gates -- another of Obama's "Team of Rivals" war cabinet who detonated his own memoir on the bestseller lists last year.

Gates complained Obama didn't even believe in his own strategy to surge troops into Afghanistan -- forcing the president to answer awkward questions in an Oval Office photo op.

- 'Cautious and indecisive' -

Both Gates and Panetta leavened their criticism of the president's political and strategic vision with praise for his intellect and gutsy call to take out Osama bin Laden.

But it is their criticism that makes headlines because the authors, with nearly a century in Washington between them, are seen by journalists as highly credible; and their complaints solidify existing perceptions of the president.

Many close observers of Obama see him as a professorial, overly cautious and even indecisive leader, who abhors the dirty business of politics which presidents like Lyndon Johnson and Bill Clinton adored.

So pervasive is this narrative that the president himself lampooned Washington's amateur political psychologists, when he was quoted as saying in a recent New York Times article "Oh, it's a shame when you have a wan, diffident, professorial president."

The White House sees no point in getting into a shouting match with Panetta that would give his story legs.

Obama spokesman Josh Earnest pointed to Obama's leadership on issues like the Islamic State group and the Ebola crisis, and said Panetta should consider whether it was appropriate to write a tell-all with Obama still in office.

Vice President Joe Biden, meanwhile grumpily rebuked former colleagues who "as soon as they leave, write books, which I think is inappropriate."

Privately, some White House officials expressed surprise at Panetta's apparent lack of loyalty.

But others were not shocked that such a savvy operator would not wait to put his mark in history and would move at his moment of maximum earning potential.

- Treachery -

This is not the first White House to fret at Washington's memoirists.

President George W. Bush's inner circle regarded a 2008 book by his former press secretary Scott McClellan, as open treachery, after he said the president was guilty of "self-deception."

Earlier, former Treasury Secretary Paul O'Neill painted a deeply unflattering picture of a callow Bush for his biographer Ron Suskind.

Bill Clinton suffered when his young aide George Stephanopoulos, asked in his 1999 book how a president he saw as public spirited and conscious of his place in history, could behave in such a "stupid, selfish and destructive" way by having an affair with a White House intern.

Perhaps the classic of the genre came from former White House chief of staff Donald Regan who turned on Ronald Reagan and his wife, Nancy, by revealing she used astrology to plot her husband's schedule.

In the end, many explosive memoirs have a limited shelf life because the juicy bits are surrounded by pages of turgid prose on the mechanics of governing.

Such may be the fate of former secretary of state Hillary Clinton's recent book, which although she uses it to distance herself from Obama's Syria policy, is hardly a tell-all. In fact, "Hard Choices" was panned by some critics as boring.

But Clinton, unlike Gates and Panetta, who are comfortably retired, has no incentive to dish the dirt on Obama -- because she needs him if she is to capture the White House herself.

The president meanwhile may have the last laugh.

The biggest literary sensation of the Obama years will surely be his own post-administration memoir.

And the list of scores he has to settle is getting longer by the month...