Last year 72 London babies were identified with permanent deafness
Hundreds of newborns in London are missing out on vital hearing tests, a hearing charity says.
The National Deaf Children's Society (NDCS) rated the capital as the poorest performer in England.
The NDCS found that only 11 of 32 Primary Care Trusts (PCTs) met the government target to screen 98% of newborns within a month of their birth.
The worst performer was Southwark with only 59% of babies tested, followed by Lewisham at 65% and Lambeth at 67%.
NHS London, which oversees all of the city's PCTs, said it will monitor the progress of the three boroughs closely.
NDCS, which campaigned to introduce the NHS Newborn Hearing Screening Programme, said all children should be tested soon after birth.
But London was far below the national average with only 72 children identified with permanent deafness in 2007-08 instead of the expected number of 140.
The performance also differed from borough to borough, with Bexley and Havering topping the table with 99%.
The period of time a family had to wait before an audiology assessment also differed with Camden, City of London and Hackney boroughs leading with 95% of babies checked within six weeks of the referral.
Suzanne Sibillin, NDCS regional director for London, said: "The NHS must take urgent action to ensure that all newborn babies in London benefit from screening and the appropriate aftercare."
NHS London chief nurse Trish Morris-Thompson said: "Clearly the performance across the majority of London PCTs is not delivering the level of care we would expect.
"The three lowest performing PCTs (Lambeth, Southwark and Lewisham) have a comprehensive action plan in place to raise the standard of service and we will monitor them closely as they progress their action plan and intervene if necessary."