London Mayor Sadiq Khan admitted he cannot put a figure on the number of affordable homes he can build each year.
After being questioned by the London Assembly for the first time since assuming the position, the Labour Mayor said he has not got a yearly target for how many will be built.
In the first Mayor's Question Time, Khan said he will instead focus on building "the right kind of homes".
He told Assembly members: "I'm not giving numbers, and during the campaign I was quite clear - when all the other candidates were throwing around figures - it is making sure the right sort of homes are built rather than an obsession with numbers.
"Let me tell you why. It is possible to build 50,000 new homes a year, some people say, but there is no point if they are all built by investors in the Middle East and Asia and they are used as second homes or sit empty."
He added: "The important thing is to build the right sort of homes ... that are affordable to Londoners to buy or rent. That is what I intend to do."
In his first fortnight in the post, Khan said former Conservative Mayor Boris Johnson had "left the cupboards bare" regarding the housing crisis.
"Boris Johnson has left affordable housing delivery in London hanging in the balance.
"Last year a mere 13% of approvals were for affordable housing.
"I'm determined to turn around this pitiful record of affordable housing delivery which falls woefully short of meeting Londoners' needs."
He added: "My long-term target of 50% of new homes to be genuinely affordable is crucial to ensuring this step change.
"I am confident this can be achieved without reducing housing supply. I'll be using public land, my investments and my full suite of planning powers to ensure London builds more affordable homes."