Boris Johnson and his girlfriend Carrie Symonds will move into Downing Street later today, officials have confirmed.
A spokeswoman for the prime minister said: "The PM is officially moving in today and, yes, his partner will be living there."
She added "there won’t be any additional cost to the taxpayer" from Ms Symonds living in Downing Street.
Ms Symonds, a former head of communications for the Tories, is set to become Downing Street’s first live-in girlfriend.
Officials suggest Ms Symonds will not be employing any publicly funded staff.
The pair will be moving into the flats above Number 11 Downing Street rather than Number 10.
The move comes as Mr Johnson heads to Scotland today for his first trip to the country since taking office in a bid to "renew the ties" between the UK’s four nations.
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A survey by Deltapoll for The Mail On Sunday showed opinion was evenly divided on whether Mr Johnson’s partner should live with him at the prime minister’s official residence.
Some 33% backed the pair living together, while the same number were opposed to it.
Mr Johnson previously refused to address whether his girlfriend would be joining him in Downing Street, saying: "I don’t want to get into any kind of presumptuous theorising about living in Downing Street at all."
The prime minister split from his second wife Marina Wheeler last year and had been living with Ms Symonds at her flat in Camberwell, south London.
He faced questions about his personal life throughout his leadership campaign, which came to a head when police were called to their London flat after neighbours reportedly heard a row.
Officers were alerted after neighbours heard screaming, shouting and banging, according to a report by The Guardian.
Mr Johnson would not address the incident when asked about it during his campaign.
The pair were later seen holding hands in photographs said to have been taken the weekend after the incident, but some people were suspicious they appeared staged.
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The incident did not seem to significantly damage Mr Johnson’s chances of becoming prime minister, with a Sky Data poll finding half the public believed it was not relevant to his suitability to be leader of the country.
Some 51% thought it was irrelevant, while 39% thought it mattered and 10% were not sure.
The subject of whether Ms Symonds would join the prime minister in Downing Street also attracted much media speculation.
The Daily Mirror reported a split in Mr Johnson’s team, with some wanting him to enter the official residence alone.
Removal vans were seen outside Downing Street last week as Theresa May left the property.