Sir Trevor Brooking yesterday pitched in against the loss of playing fields which has left grassroots sport in a "dire state".
Many facilities being almost unusable, limited access and local authority squabbles about land use have hampered the quest for health and fitness, said the former West Ham and England star.
Poor quality coaching for the crucial five to 11-year-old age group is also damaging chances of success.
"For 20 years we have moaned and groaned about the state of playing fields," the Football Association's director of development told a London Assembly conference.
"We have to protect what is out there, but we have to accept that it is in a pretty dire state. Health is the current hot potato and the health service would not be able to cope in 10 or 15 years if we do not get a much healthier younger generation."
Sir Trevor, a fierce opponent of development on playing fields, also stressed the importance that facilities and coaching can have in sports development.
He said: "How can you improve this. The ideal area is quality coaches. All the worst, least paid, least qualified coaches are working in the five to 11-year age group. In other countries they are investing in quality coaching.
"If you do not introduce a youngster to a decent, fun, quality experience by the time they are five to 11 years old, I can guarantee you that by 11 you have lost them." Just over three per cent of the playing fields in the country are in London and 16 per cent of the population live in the capital.
"It does not take a mastermind to know there are not enough spaces to give everyone the chance to play the game," Sir Trevor argued.
Only three per cent of Londoners between 6 and 44 play regular sport - 30 per cent below the national average.