Diane Abbott says she is intending to put herself forward to become Labour's candidate for Mayor of London in 2016.
The MP for Hackney North and Stoke Newington told ITV London she would run as a "genuinely independent candidate" who would oppose "anti-immigrant propaganda".
Ms Abbott unsuccessfully contested the Labour leadership in 2010.
Tottenham MP David Lammy and ex-culture secretary Dame Tessa Jowell have also expressed an interest in the candidacy.
And transport expert Christian Wolmar says he intends to put himself forward as a candidate for the Labour nomination.
Ms Abbott said: "A great many people have been pressing me for some time to throw my hat in the ring.
"In the end I decided that because London needs a genuinely independent candidate, London needs a candidate that will fight to make London more affordable for ordinary Londoners."
"I also think London needs a voice that will stand up against some of the anti-immigrant propaganda that we're hearing."
Diane Abbott's career
In August the current Mayor of London, Boris Johnson ended months of speculation by saying he would seek to become an MP again at next year's general election, although he promised to see out his current term as mayor, which ends in 2016.
Ms Abbott's announcement comes days after former BBC Newsnight host Jeremy Paxman said he had been approached to become a Conservative candidate for the post.
But he said he decided he would not enter the running to replace Mr Johnson "for all the eclairs in Paris".