More than half of the capitals major A&Es failed to meet the Government's four-hour waiting time target.
Six London trusts missed the target at least 80 per cent of the time over the last year, while Barking, Havering and Redbridge University Hospitals Trust missed it every single week.
The London Assembly's Health Committee, which carried out the study, warns that waiting times could get worse this winter as demand for care increases.
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Pictures of today's events unfolding following a major security incident at the Houses of Parliament.
At least two people have died after a knifeman brought terror to the heart of Westminster.
The Cobra committee brings together government ministers with senior officials of the emergency services and security agencies.