Homebuyers need to find a deposit of nearly £26,500 to buy the average home in England and Wales, according to figures from a housing investment and shared-equity mortgage provider.
The research by Castle Trust also shows the ever-growing divide between property prices in the north and south of the country, with buyers in London needing five times the deposit of those in Blackburn.
Analysis of 30 cities in England and Wales shows the average deposit needed to put down 20% of the purchase price is £26,468, but regional disparity means it is £72,760 in London and £14,470 in Blackburn.
The second most expensive place to secure a house is Reading with an average deposit of £39,789, while the second cheapest is Blackpool with £15,707.
Sean Oldfield, chief executive at Castle Trust, says: "Parents and grandparents are being called on more and more to help children with their first deposit and the proportion of the population owning their own home without family help is likely to continue to fall."
He says government initiatives such as NewBuy and FirstBuy, which aim to help people purchase property, need to be backed up by private companies offering support to buyers.