A senior minister has disputed claims Sue Gray was pressured to water down her report into law-breaking parties across Westminster, saying he is “confident” the investigation had been entirely independent. Brandon Lewis, the Northern Ireland secretary, dismissed suggestions that senior figures in Downing Street pushed for detail about the so-called “Abba party” in Boris Johnson’s flat during lockdown and staff members’ names to be stripped out. The allegations were reported in the Sunday Times, which said Gray was lobbied to alter key passages of her report on the eve of its publication by three people: Steve Barclay, the prime minister’s chief of staff, Simon Case, the cabinet secretary, and Alex Chisholm, the permanent secretary for the Cabinet Office. Earlier in the week, the Guardian revealed how Tory MPs feared there had been a “cover-up” over the Abba party, which Gray has admitted she did not fully investigate. Lewis did not explicitly deny that Gray had been pressured into changing her report because he said he was not involved in the inquiry, but said “anybody who has worked in No 10” knew that “that kind of thing wouldn’t work”. He told Sky News’s Sophy Ridge On Sunday: “I’m confident, particularly now that No 10 have outrightly made the point and denied that this happened, that Sue Gray had the freedom to write the report that she was comfortable to write and publish.” Given the Metropolitan police did not issue any fixed-penalty notices for the event, Lewis said this “backed up” Downing Street’s denial of the story. Asked how the media and the public could trust No 10 after it initially denied Covid rules were broken, Lewis said: “It is a different Downing Street, you’ve got a different team of people, the chief of staff is different – the team you’re talking about who work with the prime minister, who lead on these issues. “Steve Barclay himself is new and wasn’t there at the time of those original mistakes.” Johnson will probably face further headaches, given his former top adviser Dominic Cummings said evidence of “crimes in the flat” where Johnson lived had been ignored by the Metropolitan police and Cabinet Office. Labour said Johnson needed to explain why figures in No 10 “interfered in an investigation he had claimed was independent and leant on Sue Gray”. Angela Rayner, the party’s deputy leader, said: “It’s about time the public were told the truth, but this prime minister can no longer be trusted to tell it.” Johnson faces an investigation likely to begin next month into whether he misled parliament by denying for weeks that any Covid rules were broken. Anneliese Dodds, the Labour party chair, said not enough Conservative MPs had decided yet whether to try to depose Johnson or put the Partygate scandal behind him. “We think that ultimately politics should be clean, it should be a force for good,” she said. “We should have all politicians held to high standards.”