White House chief of staff John Kelly may have had his personal mobile phone compromised as long ago as December 2016, according to three US government officials, Politico reports.

Tech support staff at the White House found a potential breach after Kelly submitted his phone, claiming it hadn't been working properly for months and would not update software. Officials do not know the time or location of initial compromise, or the data that may been accessed. After their review, they concluded the phone should not be used due to a potential breach.

Kelly had reportedly avoided using his personal phone since joining the White House in January, instead relying on his government-issued phone for official communication. His travel prior to January is under review. Kelly has begun using a different phone but uses his government phone inside the White House, according to the report.

The discovery of a potential breach has sparked concern that hackers or foreign governments may have been able to access information on Kelly's phone during his term as secretary of Homeland Security and after he joined the White House.

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