The dramatic downfall of CIA chief David Petraeus has given rise to political intrigue in Washington as a drip-feed of details concerning his clandestine affair mixes with serious questions over the timing of the resignation.

Over the weekend it emerged that his relationship with biographer Paula Broadwell was discovered by FBI agents while they investigated harassing emails she allegedly sent to a second woman, the identity of whom has yet to be revealed.

The scandal comes at a particularly sensitive time. Petraeus had been due to give evidence before a Congressional body this coming Thursday concerning the attack on the US consulate in Benghazi in which four Americans were killed, including America's ambassador to Libya, Chris Stevens.

It is now thought that Petraeus will not attend the session, robbing politicians of the opportunity to question an "absolutely necessary witness", according to Peter King, chairman of the House homeland security committee.

White House and intelligence officials have suggested that there is no connection between the timing of Petraeus's resignation and the evidence session on the Benghazi attack.

But in Washington, questions are being asked as to why the FBI appeared to have sat on the information it uncovered regarding the affair before handing it on to other authorities some time later.

Intelligence officials have suggested that Petraeus was first questioned over the nature of his relationship with Broadwell a fortnight ago.

But it was only on the night of the presidential election that national intelligence director James Clapper was notified of the affair. It is thought that Clapper then advised the CIA chief to resign.

Even then, it was not until the next day that the White House was informed of the situation. It then took a further day before newly re-elected President Barack Obama was told that his intelligence chief was to tender his resignation.

Meanwhile, the Senate intelligence committee only heard about the matter on Friday, just hours before the CIA director announced he was to step down.

Further confusing the time-line of events were reports on Sunday that leading House Republican Eric Cantor had been informed by an FBI whistle-blower of the brewing Petraeus scandal two weeks ago.

If true, it would raise the prospect that the affair had become known in Washington circles before Friday's resignation.

House Republican King said on Sunday that the account of who knew what and when "doesn't add up", saying that there were a lot of unanswered questions.

The FBI had an "obligation" to tell the president as soon as they had identified a possible security breach, he told CNN's State of the Union.

Meanwhile, other politicians said that Petraeus may still be compelled to give evidence concerning the 11 September attack in Benghazi.

"We may well ask him," Senator Dianne Feinstein, chair of the Senate Intelligence Committee, told Fox News Sunday.

Congress is keen to question the former four-star general over what the CIA knew in advance of the assault, and importantly, what it had told the White House in regards to the nature of the terrorist threat.

In the run-up to last week's election, senior Republicans accused the White House of misleading Americans over claims that it was not made aware of requests to bolster security in advance of the assault.

It is on this point that Petraeus was expected to be questioned at Thursday's Congressional hearing. Following his resignation, it is thought that his former deputy, Michael Morell, will testify before Washington in his place as acting director of the CIA.

Morell is slated to meet with Congressional figures on Wednesday to discuss the Petraeus affair in a bid to curtail lingering suspicions over the timing of the resignation.

The political fall-out from Friday's resignation comes amid a personal crisis for a man often referred to as the leading American military mind of his generation.

In the days following his announcement to step down, a steady flow of leaks to the US media have given more detail to the affair that cost Petraeus his job.

The makings of his downfall were in a series of apparently vicious emails sent by his lover — a 40-year-old former Army reservist who co-authored All In, a fawning biography of the CIA chief — to a second woman.

It is thought that the threatening nature of the missives led the recipient to seek the protection of the FBI.

An investigation of Broadwell's personal email account uncovered letters of an explicit nature between her and Petraeus, who has been married for the past 38 years to his wife Holly.

It was then that agents approached the CIA chief directly. Having eliminated the threat of a security breach, it was decided that no further action would be taken by the FBI.

But the damage to Petraeus's reputation was clear, and having consulted with Clapper, the decision to resign was made.

In a letter to staff explaining his move, the now outgoing CIA boss said: "Such behaviour is unacceptable, both as a husband and as the leader of an organisation such as ours."

Others close to Petraeus had an even more blunt assessment of the scandal. "He screwed up, he knows he screwed up," said Steve Boylan, a retired army officer and Petraeus's former spokesman. © Guardian News and Media 2012