Labour has criticised Boris Johnson as a "part-time" mayor amid continued speculation that he will return as an MP before the end of his current term.
Renewed speculation in newspapers today suggested that Mr Johnson would announce his intention to stand for parliament at next year's general election by the summer.
A Labour source said the party would attack the mayor if he to "further his own political interests at the expense of the needs of Londoners".
Shadow justice secretary Sadiq Khan tweeted: "Wouldn't it be great if London's part-time mayor cared about our future as much as he cares about his own?"
Former mayor Ken Livingstone added: "Whether Boris Johnson is an MP, in the House of Lords or wherever it will make no difference as he doesn't do the day job as it stands, he leaves it to all his deputies."