The number of patients forced to wait in ambulances at A&E departments for more than half an hour rose to 11,100 last week, figures show.
Of these, 2,100 patients had to wait more than an hour to be seen after arriving at hospitals in England.
Weekly statistics released by NHS England show ambulance delays of between 30 and 60 minutes were up from 11,000 the previous week.
There were 43 incidents of ambulances being turned away from A&E departments and having to divert to others, compared with 20 the previous week.
NHS England said a broken CT scanner at one hospital accounted for many of these as patients had to be sent to other hospitals.
Flu and norovirus are continuing to put a strain on services, with 155 confirmed flu-related deaths this winter.
NHS data shows a fall in the number of bed closures due to norovirus or diarrhoea and vomiting, from an average of 742 per day to 672, but reports of norovirus remain above the five-year average for this week.
An NHS England spokesman said: “Raised levels of flu and norovirus cases continued to put pressure on busy hospitals and other frontline services last week.
“And while the NHS is generally coping with ongoing winter demands, the public can continue to play their part by using NHS 111 and pharmacists for advice.”