More than a third of Ealing's five-year-old children are failing to meet expected standards.
That's according to new analysis by the House of Commons Library on behalf of Labour candidate for London Mayor Tessa Jowell.
The research shows in 2014, 1,665 Ealing children – or 36% of the total – failed to achieve the expected level of development aged five.
London-wide, nearly 40,000 five-year-olds were found not to have achieved the standard expected by the Government’s Early Years Foundational Stage framework.
The framework measures children across five disciplines at the end of the school year in which they turn five – normally, but not always, reception year - with a minimum standard across each required to pass.
The five disciplines are: communication and language; physical development; personal, social and emotional development; literacy; and mathematics.
There are 14 boroughs in which at least two in five London children are failing to achieve a "decent" standard.
In London, 23,420 (22%) failed to achieve a decent standard of communication and language, and 18,890 (18%) failed on personal, social and emotional development, while 33,140 (32%) failed on literacy, and 26,990 (26%) failed in maths.
A recorded 38% of London boys did not achieve the expected level of development in literacy compared to just 25% for girls.
Boys lagged behind girls across all the measures, with the largest gap in personal, social and emotional development, with 24% of boys failing to meet the expected level compared to 12% of girls.
Ms Jowell said: “We should all be shocked and galvanised to action by these figures which tell a story of too many Ealing children beginning on a path that will take them to a lifetime of inequality and denied opportunity.
“What is even more shocking is that this waste of potential can be prevented by support for very young families and children in the first 1,000 days of their life to ensure that when they get to school they are ready for school and ready to learn.
“That’s why if I become Mayor of London I will act immediately to restore Sure Start to its founding purpose and ensure every child has every chance.”