Experts have warned that Boris Johnson's administration is more corrupt "than any UK government since the Second World War".
Researchers at Sussex University's Centre for the Study Corruption warned that the "absolute failure of integrity at No 10" could have potentially serious consequences for the UK if allowed to fester.
It comes as opposition figures warned of the "appearance of an establishment stitch-up" over an inquiry into rule-breaking at Downing Street.
The Metropolitan Police on Friday said it had asked civil servant Sue Gray to remove key details of potential illegality from her long-awaited report into the Partygate scandal - citing a need not to prejudice its own separate investigation.
The development means some aspects of behaviour at Downing Street may not be made public at a key moment of political danger for the PM – and even raises the prospect that some facts might never see the light of day at all.
Robert Barrington, Professor of Anti-Corruption Practice at the Centre for the Study of Corruption in the University of Sussex said: "There is more corruption and corruption risk in and around this government than any UK government since the Second World War.
"The PM has direct influence on this through personal example and through what he allows amongst his Ministers and No. 10 staff.
"There has been an absolute failure of integrity at No 10 which has consequences for democracy and Britain's global influence - and longer term, if unchecked, for the economy and national security.
"The enablers of this are any MPs or Ministers that allow the failure of integrity to go unchecked. But - although standards have slipped, they can still be restored, if there is the political will to do so."
The latest row over the Partygate inquiry came just 48 hours after new evidence suggested that the prime minister misled the public over his role prioritising the evacuation of animals from Afghanistan last year. He had previously denied any involvement.
The prime minister has also found himself embroiled in a scandal over private donors financing a lavish refurbishment of his private Downing Street flat.
And last year the government was forced to back down after it moved to abolish a standards watchdog which had recommended mild sanctions against a Tory MP who broke lobbying rules.
Dr Sam Power, a lecturer in corruption analysis at the anti-corruption centre, said: "We didn't really need a detailed inquiry to know what Partygate is. Either having a party, or indeed a work event, is in blatant contravention of the rules as written, and the commonly understood way in which the British public was expected to behave during the height of the pandemic.
"Partygate is indicative of Johnson's reckless approach to the rules and the kind of behaviour that the public expects of those in the highest office.
"Whilst this cavalier approach to ethics is, in part, baked into his wider electoral appeal his standing is now damaged beyond repair with the British people.
"Whether Conservatives decide Gray's report is enough to warrant a change of leadership, is an open question. But his standing is now so damaged with the voters that MPs may well consider if one of Johnson's core strengths, his electability, is now a fatal weakness. To many, the joke simply isn't funny anymore, if it ever really was."
The Covid-19 Bereaved Families for Justice group on Friday said the the investigation into No 10 lockdown parties was becoming “circus”.
Fran Hall, whose husband served in the police for more than three decades before dying with coronavirus, accused the Metropolitan Police of letting bereaved families down.
The Met has asked for Sue Gray’s partygate report to make “minimal reference” to events it is investigating to avoid prejudicing inquiries – but this has led to criticism that the findings will be watered down.
Tory MP Roger Gale meanwhile described the latest development as a "farce created in Scotland Yard", while Liberal Democrat home affairs spokesperson Alistair Carmichael said the proceedings risked giving the "appearance of an establishment stitch-up".
"First the police were waiting for Sue Gray, now Sue Gray has to wait for the police?" he said.
"Any appearance of an establishment stitch-up between the Met Commissioner and the Government is profoundly damaging. Police officers need the trust and confidence of the public to do their jobs and keep our communities safe.
"That's why we called for the police to investigate Number 10 weeks ago and put this whole sorry business behind us, instead of waiting for Sue Gray.
"The Sue Gray report must be published in full, including all photos, text messages and other evidence. If it is redacted now, a full, unredacted version must be published as soon as the police investigation is complete."
