Ambulance waits: 'The paramedics put patient safety first'
9 December 2013 Last updated at 10:26 GMT
Barbara Hakin, deputy chief executive of NHS England, has said it is "sometimes in the best interest of patients' safety that they remain in the ambulance after they have arrived at hospital".
Some patients taken by ambulance to A&E departments are waiting in the vehicle for much longer than the recommended 15 minutes, with one case involving a six-hour delay, figures show.
Data for ambulance services in England, Scotland and Wales, obtained by the BBC under the Freedom of Information Act, suggest Wales had the longest waits.