Facts
Boris Johnson asserted that the Coalition government in the year 2010/11 built more affordable homes than the Labour government had in the years 1997-2010.
Data from the Department for Levelling Up, Housing and Communities shows that 557,217 affordable homes were built between 1997-2010, compared to 61,089 in the year 2010/11.
For a fuller analysis see this excellent analysis by Full Fact.
Verdict
A rubbish claim by Boris Johnson.
In the same speech, Boris Johnson made a false claim regarding affordable housing in London.
We approached Boris Johnson's office, No10 Press Office and the Cabinet Office to give them a chance to comment, but received no response.