A scathing report by the US State Department’s own independent watchdog asserts that Hillary Clinton trampled all the rules when she chose to use a private email server during her tenure as US Secretary of State, contradicting her long-held position that she never did anything wrong.

It said that when she was advised that her set-up might make top-secret information vulnerable to outside hacking, she ignored the admonition and that her own aides twice brushed off the concerns, once telling a technical supervisor that the matter was “not to be discussed further”.

Delivered on Wednesday to Congress, the bluntly-worded report from the office of the inspector general said Ms Clinton should have sought assistance as well as permission from the relevant cyber-security and archiving supervisors at the State Department before establishing her own server inside her home in Chappaqua, north of New York City, and that she had failed to do so.

Ms Clinton, who has been dogged by the email affair since first declaring her presidential run, failed to demonstrate that either the Blackberry she used to send and receive emails or the private server at home “met minimum information security requirements,” the report said.

The 78-page document says the then Secretary of State, “had an obligation to discuss using her personal email account to conduct official business” with those supervisors and the inspector general had “found no evidence that the Secretary requested or obtained guidance or approval to conduct official business via a personal email account on her private server”.

“Department employees must use agency-authorized information systems to conduct normal day-to-day operations because the use of non- Departmental systems creates significant security risks,” the document concludes.

Had she sought permission, she would not have received it. Department officials responsible for information management and security “did not - and would not - approve her exclusive reliance on a personal email account to conduct Department business,” the report said in its conclusions.

The unequivocal finding that Ms Clinton violated set practices and protocols when she began as Barack Obama’s diplomat-in-chief in 2009 threatens further to destablise her presidential campaign, already bruised by the assaults of the other Democrat in the field, Bernie Sanders.

While Ms Clinton has said she is sorry for any mistakes she may have made she has always fallen back on the assertion that she was never guilty of actual misconduct. “Nothing that I did was wrong,” she said during one CNN town hall conversation in January.

The report speaks of systemic problems at the State Department regarding the handling of potentially sensitive information, spanning several presidential administrations and the tenures of several of Ms Clinton’s predecessors, a point emphasised by her campaign on Wednesday.

“The inspector general documents just how consistent her email practices were with those of other secretaries and senior officials at the State Department who also used personal email,” Brian Fallon, a campaign spokesman said, noting that the report says “her use of personal email was known to officials within the department during her tenure, and that there is no evidence of any successful breach of the secretary's server.”

There is nothing in the report recommending either punishment or penalty for Ms Clinton. Nonetheless the vast bulk of it is aimed at her lapses while Secretary of State and the 30,000 email sent using the private server, even though her predecessors in the post going back to Colin Powell and Madeleine Albright also get mentions for falling short in the same area.

But its release will inevitably provide fresh fodder to her Republican foes, including the presumptive Republican nominee, Donald Trump.

The inspector general’s findings are just part of a broader shadow that the email affair continues to cast over Ms Clinton as she seeks finally to dispatch Mr Sanders in her bid for the Democratic Party presidential nomination and pivot to start attacking Mr Trump.

Potentially more ominous for her is the ongoing FBI investigation into whether her choices while Secretary of State meant that classified information was made vulnerable to outside hacking. She has consistently said that nothing she sent or received contained content that has been designated as top secret or classified.

There is also a looming civil lawsuit that could oblige the former first lady to testify in court on the matter and several Republican-led committees on Capitol Hill are planning new hearings into the affair this summer, ensuring it stays in the headlines through the presidential race.

Among those interviewed for the report were both Ms Albright and Gen. Powell as well as Condoleezza Rice, who also served George W. Bush. It notes however that Ms Clinton declined to be interviewed as did some of her top advisors at the time, Cheryl Mills, Jake Sullivan and Huma Abedin. Ms Abedin remains at her side in her presidential campaign.

In criticising the State Department in general for its shortcomings, the report said it had been “slow to recognise and to manage effectively the legal requirements and cybersecurity risks” that emerged in the era of emails, particularly where top officials like Ms Clinton were concerned.

Republicans in Washington were quick to pounce on the report’s findings as vindication for their long effort to hold Ms Clinton’s feet to the fire over the whole email affair.