Many more younger UK households face a "yawning gap" in the market for affordable housing than previously thought, states a new report.
Young buyers can't afford to get on the property ladder
Young households are too poor to buy the cheapest local houses, but would be too rich to qualify for housing benefit.
And there is a serious shortage of moderately-priced rentals, it says.
The report was published by social policy research charity the Joseph Rowntree Foundation.
About 1.2 million younger households in England, Wales and Scotland are caught in a "yawning gap in the market": unable to buy a first home, but not eligible for housing benefit.
The report's author, Professor Steve Wilcox of the University of York, called for "new and creative thinking" on ways to meet the needs of another 60,000 newly-formed young households each year.
The report estimates that just under one fifth of households aged under 40 are affected by the problem, rising to half in the worst-affected areas.
It identifies 40 districts where 40% or more of young working households were unable to afford the 10% of cheapest two- and three-bedroomed houses.
All but one of the 40 worst areas are located in the South, with property least affordable in Weymouth and Portland, where 55% of young working couples could not afford a first home.
Fourteen of the local authorities on the list are in the South East, 13 are in London and 12 are in the South West.
Ryedale, in North Yorkshire, is the only "worst-affected" area listed outside the South.
The overall ratios of house prices to working household incomes were at record levels across the country, the report finds.
In 33 districts, local property prices are more than five times higher than the average income for young working households.