The Red Devils were unaware that a police report for an alleged assault by the Brazilian on a woman had been filed more than three months before he signed for £85 million ($105.2m) from Ajax in September last year, according to The Telegraph.
The report states that Rayssa De Freitas lodged the complaint to Sao Paulo Civil Police in May 2022, where she alleged she was attacked by Antony and a woman and required hospital treatment after an argument in a car following a night out in Brazil.
United have reportedly said they carried out 'due diligence' checks on the winger but found no evidence of domestic abuse allegations or police involvement regarding his past.
The Telegraph also states the club only became aware of the police report following news coverage in Brazil this month, when they were shared by the 23-year-old's representatives.
Antony is currently on paid leave from the Manchester outfit while he fights allegations against him.
His ex-girlfriend Gabriela Cavalin claimed the Brazil international subjected her to a number of attacks between June 2022 and May 2023. He denies any wrongdoing.
United's due diligence checks also failed to pick up that former defender Marcos Rojo was being investigated by police for an alleged bottle attack on two men in Argentina before they signed him from Sporting Lisbon in 2014. The Argentine settled out of court and the case was dropped.
Moreover, it also emerged that Geoff Konopka, the first manager of United's women's team between 1983-2001, was a special guest at a game at Old Trafford last year - despite being a convicted paedophile and having an active suspension on the Football Association's safeguarding system.
He spent four years in prison in 2011 and was placed on the sex offenders' register for a decade, after being convicted of 19 offences of gross indecency and indecent assault against girls aged 14 and 16.