999 patients awaiting treatment at the Norfolk and Norwich University Hospital were left in queues for up to three hours or more – and then faced the prospect of being treated in a tent if the hospital could not take them in.The East of England Ambulance Service (EEAS) put up the 'major incident tent' yesterday for the first time outside the N&N.

This action was taken during a nine-hour period where an average of between six and 15 vehicles were queuing outside the Colney hospital's accident and emergency department.

The latest incident follows similar problems last month when 17 ambulance crews were left waiting outside the N&N.

In any given month, 80pc of patients should be handed over to the N&N within 15 minutes of their arrival by ambulance. EEAS said yesterday's delays prevented vehicles responding to other patients.

The tent would have allowed patients to have been off-loaded and receive treatment outside the N&N, in order to release ambulances back on to the road.

EEAS workers say it is unheard of for the tent to be placed outside an A&E department, and it is usually reserved for major emergencies such as train or plane crashes.

Norwich North MP Chloe Smith also called for an 'urgent explanation' from all authorities as to how they will work together to put the handover problems right 'once and for all'.

Both the N&N and EEAS said the tent was ultimately not required despite the long delays.

Oskan Edwardson, EEAS' associate director of special operations, told the EDP last night: 'Between 11am and 8pm the trust had an average of between six and 15 vehicles queuing for up to three plus hours.

'Clearly this led to ambulances not being available to respond to other patients in the community.

'We worked closely with the hospital and clinical commissioning group throughout the afternoon and deployed the trust major incident tent to help release ambulances back on to the road.

'The trust is pleased that this issue is now resolved following much hard work by the hospital and the ambulance service and that in the end no patients were required to be treated in the major incident tent at this time.'

One long-serving ambulance service worker, who did not wish to be named, said: 'Road crews are so fed-up with getting slated and being made to look as if the ambulance service is to blame for the delays – but it's not, it's A&E.

'They [the ambulance crews] want to get out and save lives. That's all they want to do and they are getting caught up in a political row.

'The tent is usually used at plane crashes and big events, such as the Lord Mayor's parade. To put it up outside A&E is unheard of.'

Another EEAS worked, who also wished to remain anonymous, said of the major incident tent and associated facilities: 'When there's a massive train crash, that's when these vehicles are used – not for an A&E department.

'The tent will usually have in it treatment bays, drugs, oxygen, the same stuff on board an ambulance but inside a tent – which is a lot colder. It's a mini-hospital in a tent.'

There had been suggestions a major incident had been declared outside the N&N but this claim was denied by EEAS. An EEAS spokeswoman added yesterday: 'It is the first time such action [use of the major incident tent] has been taken. Our workload in Norfolk/Suffolk has been busy but manageable today.'

The latest incident follows similar queuing issues last month when 17 ambulance crews were left waiting outside the N&N. This meant they were unable to attend 12 other 999 calls because of the long delays. As a result, other ambulances had to be drafted in from further afield.

Anna Dugdale, Norfolk and Norwich University Hospital chief executive, said yesterday: 'The demand on emergency services over the bank holiday weekend has been exceptionally high and the ambulance tent was erected for a short period this afternoon as a precautionary measure. In the event it was not needed and has been stood down.'

More than 10 emergency vehicles were at the N&N at around 7.30pm yesterday. These included ambulances and parademic response cars.

Chris Cobb, director of medicine and emergency care at the hospital, has previously said the hospital should be able to cope with 15 ambulances turning up at once.

Last month it also emerged the N&N could be hit by fines of up to £3.5m a year for its slow ambulance turnaround times.