Jenny Jones made the pledge during a campaign visit to Stockwell, South London where she launched her accessibility manifesto.
At present just 63 of the Tube’s 270 stations are step-free from street to platform.
The Green campaign says former Mayor Ken Livingstone and incumbent Boris Johnson have both failed to meet their own targets for boosting the number of step-free stations.
Other measures outlined today include ensuring 15% of new homes are wheelchair accessible and a pledge to ensure the 100% of all bus stops are accessible by 2018, a key demand of disability rights campaigners.
Launching today’s manifesto, Jones said: “We need to aspire to an inclusive transport system, where no one is prevented for using London’s public transport.
“In the year that the Paralympics will be held in London it is shameful that the overwhelming majority of the tube system is still inaccessible to hundreds of thousands of people. This is nothing short of transport apartheid.
Other candidates for Mayor include Brian Paddick (Liberal Democrat), Ken Livingstone (Labour), Lawrence Webb (UKIP) and Boris Johnson (Conservative). Mr Johnson’s campaign declines to provide policy details and campaign announcements to this site.
