LONDON — Boris Johnson, in his fourth day as London mayor, asked 700 City Hall staff to stay on the job, saying he’s not that different from his predecessor, Ken Livingstone.

“The differences between me and the previous mayor of course have been greatly simplified and greatly exaggerated,” Mr. Johnson told reporters yesterday. “We do have different political philosophies but that doesn’t mean there aren’t huge areas of common ground between me and ex-mayor Livingstone.”

Mr. Johnson, 43, a Conservative member of Parliament and journalist, took over on May 3, two days after he defeated Mr. Livingstone, a two-term mayor and member of Gordon Brown’s Labour Party.

He’s in the process of putting together a staff that will guide his next four years in office. He has picked four deputy mayors so far and said he would name other top aides in coming days. Appointees include Richard Barnes, a Conservative member of the legislative assembly as deputy mayor; Kit Malthouse, a newly elected Conservative assembly member as deputy mayor for policing; and Ian Clement, a local official in the district of Bexley, as deputy mayor for government relations.

Every city program is being evaluated to ensure it offers “value” to London taxpayers, he said. The British capital, the largest city in western Europe, has a $22 billion annual budget and 7.5 million residents.