Sadiq Khan has questioned NHS plans to transform health services in the capital and called for more powers to oversee the changes.
It follows an independent review which has raised concerns about how joined up current proposals are, and whether or not they're financially viable.
London has been divided into five regions, each with a Sustainability and Transformation plan (STPs) developed by the NHS that aim to improve care.
A study by The King's Fund and Nuffield Trust says greater city-wide leadership is needed - ideally from the Mayor - to complete the plans.
They say the government must give key assurances including more money, beds, and staff if they are to work.