Congressional Republicans have accused the Obama administration and former Secretary of State Hillary Clinton of failing to protect US diplomats in the 2012 Benghazi, Libya, attack that killed four Americans.

LISTEN ABOVE: US correspondent Jack Tame speaks with Rachel Smalley about the report

In an 800-page report that Democrats have derided as a political vendetta, Republicans also accused Clinton, now the presumptive Democratic presidential nominee, and her staff of a "shameful" lack of response to congressional investigators looking into the tragedy and assailed Clinton's use of a private email server for official business.

The findings are sure to fuel attacks on Clinton on the presidential campaign trail, where she faces the Republicans' presumptive nominee, Donald Trump, but they do not reveal any new substantial evidence of Clinton's culpability with regard to the attack.

Clinton's campaign dismissed the report as a partisan effort to derail her candidacy, arguing that the committee had not found anything that had not been discovered by previous congressional probes.

"After more than two years and more than $US7 million in taxpayer funds, the committee report has not found anything to contradict the conclusions of the multiple, earlier investigations," Clinton spokesman Brian Fallon said in a statement, adding that "this committee's chief goal is to politicise the deaths of four brave Americans in order to try to attack the Obama administration and hurt Hillary Clinton's campaign."

At a news conference on Capitol Hill, Representative Trey Gowdy of South Carolina, the Republican chairman of the special panel, outlined what he said was a disconnect between the unfolding violence on the ground in Benghazi and the perception among top Obama administration officials that "the fighting had subsided" at the US diplomatic compound.

Gowdy said the panel uncovered "new information on what happened in Benghazi," including details contained in emails from then-Secretary Clinton that were handed over to the committee.