Ambulance crews in the East Midlands say they have been busier then ever before during the Christmas period.
East Midlands Ambulance Service (EMAS) dealt with 868 Category A (life-threatening) calls on Christmas Day - a rise of 21% compared to last year.
Keith Sharpe of EMAS said a rise in flu cases and winter-related illness was behind the increase.
He said: "There has been a marked increase in flu-like illness over the Christmas period."
He added: "This is affecting resource availability and putting the whole service under increased pressure."
The public are being advised to be responsible regarding 999 calls and make full use of their GPs and walk-in centres to help ease pressure.