Single first-time buyers and England and Wales need 13 years to save for a deposit - rising to his 46 years in London.
Yet the time to save a deposit has actually fallen by nine months in England and Wales since 2014 as affordability slightly improves.
The findings are published in a new Time to Save Index launched by Hamptons International, which covers the third quarter of last year.
Hamptons said that saving for a deposit is one of the greatest barriers first-time buyers face when trying to get on the property ladder.
Single first-time buyers will take 13-and-a-half years to save a 15% deposit, 30 months longer than in 1999, but nine months faster than in 2014.
The North East continues to be the quickest place to save for a deposit with single buyers facing a wait of less than eight years.
Pooling resources with a partner or friend cuts the time to save significantly. It takes an average couple working full-time, three-and-a-half years to save a deposit for a home, eight years in London and only two in the North East.
Lending criteria has softened a little and Help to Buy also makes a difference.
Only having to save up 5% thanks to an equity loan from the Government would cut seven-and-a-half years from the time to save for single first-time buyers.
The £3,000 Help to Buy ISA bonus will cut the time a single first-time buyer has to save for by between nine to 12 months.
The Lifetime ISA announced in the Budget will have an even greater impact, cutting the waiting time for first-time buyers in England and Wales by three years, and 19 years in London.
Fionnuala Earley, residential research director at Hamptons International, said affordability is still difficult for first-time buyers but things did improve in 2015.
“House price growth slowed in England and Wales while wages increased, making it easier for first-time buyers to save up a deposit to buy their home.
“But it takes almost twice as long for a Londoner to save up a deposit now as in 2008.”