10 Downing Street struggles to cope with the demands of a modern prime minister, Tony Blair has suggested.
Mr Blair will leave Downing Street on 27 June
In an interview for the Downing Street website Mr Blair said that the building "perched a little uneasily" between national symbol and busy workplace.
The building has been the official residence of the British PM since 1732.
But while 19th Century prime minister William Gladstone had only "a few secretaries", Mr Blair said he had to have a couple of hundred people.
"That's the modern business of being prime minister," added Mr Blair, who steps down on 27 June.
He added: "Downing Street at the moment is perched a little uneasily between the formal, state, visible outward expression of Britain and the place where we receive people and so forth and a functioning workplace."
While prime ministers have traditionally lived in the private flat on the second floor, Mr Blair, his wife Cherie and their four children have lived at the larger flat above Numbers 11 and 12 Downing Street.
Chancellor Gordon Brown, who already lives in the flat above 10 Downing Street with his wife Sarah and their two sons, will take over as prime minister.
Last week removal vans arrived at Downing Street to start packing away Mr Blair's possessions, in preparation for his departure.
In the interview with the historian Simon Schama, Mr Blair said his favourite room at Number 10 had been the White Room - redecorated during Margaret Thatcher's time in office to resemble an 18th Century aristocratic drawing room.
He said he would often host meetings there with foreign leaders. "I find it the most pleasing room in the building to work in and I find it the most congenial in terms of its atmosphere."
But he said if he had a particularly tough decision to make he would go to the room next to the Cabinet room, "or sometimes... if the sun's shining, I go and sit in the garden".