One in five households in England face their homes being unaffordable by the end of this decade.
According to a study by the National Housing Federation and Pragmatix Advisory, the number of households with unaffordable homes will rise by 55%, or 1.7m, by 2030 to 4.8m.
This means the loans or rent on their homes will cost more than a third of their income, which is defined as unaffordable.
The increase includes 1.1m additional homeowners spending more than a third of their net income on a mortgage and 600,000 additional households in unaffordable private rented homes.
By 2030 2.2m households will pay a third of their income to rent privately and 700,000 in social housing.
Homelessness will soar by 130% to 620,000 people by 2045, unless politicians act, the study predicts.
