Mr Khan stood down as the party’s London and Justice spokesperson following his party’s general election failure last week.
Rival candidates for the nomination have previously accused the Tooting MP of using his position as London spokesperson to delay selecting a Mayoral running until after the general election in the hope that he’d be rewarded with a cabinet position.
Although Khan has repeatedly denied he planned a Mayoral run, it’s understood that he has been seeking internal support from MPs and councillors over the past few months.
His campaign website domain was registered in October 2014.
Speaking to the Evening Standard, Khan said he wanted to be seen as “Mr London”.
Khan was one of the architects of Labour’s London general election campaign which saw them pick up some new seats but miss a number on their target list.
David Lammy and Dame Tessa Jowell, two of Khan’s rivals for the Mayoral nomination, have have been critical of the party’s performance and warned against listening to those seeking to portray it as a success.
