Dominic Cummings has audio recordings of key discussions with senior ministers and officials, the Daily Mail quoted an unnamed ally of UK Prime Minister Boris Johnson's former chief adviser as saying on Monday.
According to the source, Cummings took a trove of material with him when he left Downing Street in 2020, including sensitive conversations in the government.
"Dom has stuff on tape. They are mad to pick a fight with him because he will be able to back up a lot of his claims. He used to tell advisers to record things all the time – discussions with officials. He has also kept a lot of his correspondence", the ally asserted.
The claims come after reports emerged on Sunday alleging that Cummings plans to point the finger at Johnson personally for the catastrophic death toll from the second wave of COVID-19 in Britain, something that BoJo's ex-top aide will reportedly present during a Commons committee gathering in late May.
The Times cited unnamed sources as claiming that "Dominic has copies of everything and knows where all the bodies are buried".
They argued that Cummings "was pushing the prime minister hard to lock down sooner in the autumn and he has lots of evidence that shows that his [Johnson's] decision to delay led to devastating consequences".
Separate reports argued that the disclosures Cummings intends to present to MPs will also include Johnson's alleged blunt remarks related to introducing restrictive measures in the UK in connection with the coronavirus pandemic.
"No more f***ing lockdowns – let the bodies pile high in their thousands!", the prime minister ostensibly said in late October 2020 after Minister for the Cabinet Office Michael Gove warned him that soldiers would be needed to guard hospitals overwhelmed with COVID-19 victims. Downing Street denied the allegations as "another lie".
The sources' claims come amid Cummings' ongoing war of words with Johnson, which kicked off after the UK PM's ex-top aide released a full-blown blog post, in which he denied leaking the details of the second coronavirus lockdown in England before it was announced.
Cummings also rejected allegations that he leaked a host of private text messages sent by UK Prime Minister Boris Johnson to tech boss James Dyson, in which the UK PM assured the billionaire that his employees would not have to pay extra taxes if they came to Britain to make ventilators during the COVID-19 pandemic.
Earlier, former Tory Prime Minister David Cameron was embroiled in a scandal after media reports said that he lobbied Boris Johnson's government on behalf of financial services company Greensill Capital to secure access to a Bank of England COVID-19 loan scheme meant to aid businesses during the coronavirus pandemic.