English first-time buyers as a whole may also see average deposits rise by nearly £20,000 to £61,291, when the deposit is 25% of the house value.

National Housing Federation assistant director for campaigns and communications, Teresa Richardson, said a whole generation was at risk of being priced out of homeownership forever and called for more homes to be built: “Where are young first-time buyers and hardworking families supposed to find the money for the safe, secure home that so many of us aspire to?”

The average first-time buyer home will rise in value to nearly £250,000 while the average first home in London may approach half a million pounds, the consultancy said.

Almost twice as many Londoners in the 25 to 34 age group now pay rent to a private landlord as those who own the roof over their heads, according to previously unpublished GLA data — and the gap is rapidly rising.

Just 202,000 Londoners aged 25 to 34 are owner-occupiers, compared with 380,000 in private rented accommodation and 110,000 social renters..