Shadow work and pensions secretary Liam Byrne today accused Boris Johnson of being a "part-time Mayor" for writing a new non-fiction book while running the capital.
Johnson's Life of London: The People Who Made The City That Made The World, out on November 3, is about "famous and infamous" Londoners who "made London what it is today", according to publisher HarperPress.
But opponents said Mr Johnson, whose other commitments include a weekly newspaper column, meant he was "not putting Londoners first".
A City Hall spokesman said Mr Johnson started the book before he was elected and insisted he completed it in his spare time. But Mr Byrne said it was "truly astonishing" he was able to write it while in charge.
He said: "Despite the summer riots, record unemployment and rising cost of living, it's clear London has a part-time Mayor...every hour Boris Johnson has spent writing his book is an hour which he could have spent working to make our streets safer and getting new investment and jobs into London."
Mr Johnson has said researching the book gave him "ideas to take forward" and "the confidence that London can continue to be the best big city in the world."
