The claims were made after “shocking” revelations were uncovered in an audit of City Hall’s ability to tackle the housing crisis.
The audit showed that only 4,880 affordable homes were delivered last year – the lowest number since 1991.
The mayor has pledged to build new homes on City Hall-owned land, including Transport for London (TfL) land, and wants to see 50% of all new homes in London being “genuinely affordable”.
Sadiq Khan commented: “London gave me the opportunity to go from the council estate where I grew up to being able to buy a family home we could afford. But today, too many Londoners are being priced out of our city.
“One of the first things we did when we got to City Hall was open the books and look at what was already in the pipeline and it seems the previous mayor has grossly let down Londoners by leaving the cupboard bare when it comes to delivering affordable housing.
“I am determined to fix London’s housing crisis and ensure that all Londoners have the opportunity to rent or buy a decent home at a price they can afford, but the scale of the challenge is now clearer than ever and we’re not going to be able to turn things around overnight.”
The mayor is set to outline plans in the coming months and will be working with TfL to fast-track its surplus sites, which have previously been sat on, for development.
“I plan to personally get to grips with the mess that has been left behind,” Khan added.
The review also uncovered an average of just 7% of national apprenticeships being made in the construction industry, despite a major skills crisis.
It was stated that only 151,000 new apprenticeships were started between August 2012 and January 2016, compared to Boris Johnson’s target of 250,000.
Khan’s housing policy was dubbed “flimsy” this week after property professionals raised concerns about whether his affordable housing targets would hinder small developers.